TONE, Circuit Judge.
The appellants were convicted, in a nine-week jury trial, of conspiring to violate the wire and travel fraud statutes and of substantive violations of those statutes.
The indictment charged that defendant Frederick B. Ingram,1 chairman of the board of the Louisiana-based Ingram Corporation, had paid defendant Robert F. McPartlin, an Illinois legislator, defendant Valentine Janicki, a trustee for the Metropolitan Sanitary District, and others more than $900,000 to secure for the Ingram Corporation a multi-million dollar sludge-hauling contract with the District. Defendants Franklin H. Weber, a businessman, and Edwin T. Bull, president of a towing company, were alleged to be intermediaries through whom many of the payments were made. William J. Benton, vice president of Ingram Corporation, was an unindicted co-conspirator who played a major role in the conspiracy and testified as a witness for the prosecution. The defendants were convicted of numerous violations of the Travel Act, 18 [1328]*1328U.S.C. § 1952, and the Wire, Radio, Television Fraud Act, 18 U.S.C. § 1343, and of conspiring to violate those acts in violation of 18 U.S.C. § 371. The jury acquitted three other defendants, E. Bronson Ingram, brother of Frederick B. Ingram and an officer of Ingram Corporation, Chester Majewski, a Metropolitan Sanitary District trustee, and Bart T. Lynam, General Supervisor of the Sanitary District.2
The defendants urge as grounds for reversal the district court’s denial of motions for severance, a ruling on the alleged withholding by the prosecution of evidence favorable to the defendants until the beginning of the trial, rulings admitting and excluding evidence, certain instructions to the jury, and other alleged trial errors. In this portion of the opinion the facts are stated and the issues arising from the denial of severance are decided. Judge Pell and Judge Sprecher have written, and I concur in, the portions of the opinion dealing with the other issues.
The Facts
The Sanitary District is a municipal corporation with primary responsibility for disposing of sewage from Chicago and surrounding areas. The District’s business is governed by an elected Board of Trustees 3 and managed by a professional staff, which from time to time makes recommendations to the Board concerning major undertakings of the District.
The Sanitary District operates a sewage treatment plant in Stickney, Illinois. Until 1971 the sludge produced as a by-product was disposed of by pumping it into nearby lagoons. Early that year, because the lagoons were rapidly being filled and efforts to clean them had failed, the District announced plans to have the sludge transported to Fulton County, Illinois, about 160 miles southwest of Stickney, and solicited bids on the project, which were due on March 19, 1971.
Viewed in the light most favorable to the prosecution, the evidence showed that Benton, acting with the knowledge and complicity of Frederick Ingram and through intermediaries Bull and Weber, bribed McPartlin and Janicki to cause the sludge-hauling contract to be awarded to Ingram Corporation and one of its subsidiaries, and later bribed the same officials to secure favorable treatment under the contract and modifications of the contract. The details were as follows:
When the District solicited bids on the-sludge-hauling project, defendant Bull assisted Frank Oberle, an employee of Ingram Contractors, Inc., a wholly owned subsidiary of Ingram Corporation, in investigating the new proposal. During the week before the bids were to be submitted, Bull visited Robert Howson, a vice president of Ingram Contractors, Inc., in New Orleans, Louisiana, and told Howson that if Ingram Corporation expected to secure the contract, it would have to make a “political contribution.” Howson responded that he was not in that sort of business, but then took Bull to meet William J. Benton, vice president of Ingram Corporation and president of Ingram Contractors, Inc.
Ingram Corporation, Burlington Northern, Inc., and the Atchison, Topeka and Santa Fe Railway Company were the leading contenders among those submitting bids on March 19,1971. To negotiate with these three bidders, the Sanitary District established a committee, which met with representatives of the bidders for the first time on March 23, 1971.
That evening Bull, Oberle, and Benton met in Benton’s hotel room, where they were later joined by defendant Weber. After Bull had introduced Weber to Benton, Bull and Oberle left the room. Weber then told Benton that if Ingram Corporation wanted the sludge-hauling contract, it [1329]*1329would have to make a $250,000 “political contribution.” Benton replied that he would have to get approval from his superiors. After agreeing to meet Benton the next day, Weber left.
Benton then telephoned defendant Frederick Ingram to inform him of Weber’s “political contribution” proposal. Ingram agreed, provided that the contribution could be added to the cost of the contract.
On March 24, 1971, Benton again met with Bull, who expressed his belief that if the Ingram Corporation accepted Weber’s proposal, it would get the contract. Bull also told Benton that if the corporation did get the contract, he wanted $100,000 in addition to anything it paid Weber. At another meeting later in the day, Weber asked Benton to open an account at a Chicago bank to demonstrate Ingram Corporation’s “good faith.” That same day, Benton opened an account at the First National Bank of Chicago.
The following week, Weber called Benton and told him that Burlington Northern, Inc. had offered to make a $295,000 political contribution. According to Weber, it was therefore necessary for Ingram Corporation to raise its contribution to $450,000, including a $150,000 cash payment before the contract was awarded. Again Benton consulted Frederick Ingram, who again agreed on condition that the contribution could be added to the contract price. Benton communicated Ingram Corporation’s approval to Weber, but said that the corporation could not raise $150,000 in cash on such short notice. Weber replied that some of the $150,000 had to be paid by April 3,1971.
On April 3, 1971, Weber and McPartlin went to Benton’s Chicago hotel room, where Weber introduced McPartlin to Benton as the man who handled all political contributions for the Democratic Party in Illinois. McPartlin assured Benton that Ingram Corporation would receive at least $21,500,000 in total revenue from the sludge-hauling contract. Benton gave McPartlin $75,000 in cash, including several one thousand dollar bills. On April 6, 1971, Weber deposited nine one thousand dollar bills in the account of one of his defunct corporations, Illinois Southern Materials.
On April 6, 1971, Weber telephoned Benton, asking for $25,000 in cash immediately to secure the cooperation of three Sanitary District staff members. When Benton protested that he could not deliver $25,000 cash on such short notice, Weber suggested that Ingram Corporation issue a check in that amount to Bull Towing Company, which Benton caused to be done the next day. On April 8, 1971, Edwin Bull deposited the Ingram check in the account of Bull Towing Company and, at the same time, withdrew $25,000 in cash from the account.
The Sanitary District requested the three bidders on the sludge-hauling contract to submit new bids by April 15, 1971. Santa Fe declined. Burlington Northern submitted a revised bid of $18,300,000. Oberle submitted Ingram Corporation’s revised bid of $16,990,000, after which he returned to his hotel room, where he received a telephone call from either Benton or Weber. The caller instructed him to go to the bar at the Continental Plaza Hotel to meet defendant Janicki, which Oberle did.4 At the meeting in the bar Janicki told Oberle to raise Ingram’s revised bid to $17,990,000. Oberle then returned to his hotel room and telephoned Benton for advise. Benton instructed Oberle to attend the Sanitaiy District negotiating committee meeting scheduled for that afternoon. While attending the meeting, Oberle received telephone instructions from Benton to raise the Ingram bid by $1,000,000 to $17,990,000. Oberle did so.
On April 22, 1971, the Sanitary District Board of Trustees voted to award the contract to Ingram Corporation. Between that date and May 12, 1971, a contract was drafted by members of the Sanitary District staff and Ingram Corporation representatives, including John Donnelly, president of Ingram Barge Company, the Ingram Corporation subsidiary that would transport the sludge under the contract. [1330]*1330The staff insisted on a liquidated damages clause authorizing the District to prescribe the amount of sludge to be transported in any 24-hour period and providing that Ingram Corporation would be assessed a penalty for each ton of sludge not transported, as prescribed, in any 24-hour period. Donnelly, after initially refusing to agree to the provision, discussed it with Benton, who told him to agree to it. Only after talking with Frederick Ingram, however, did Donnelly accede to inclusion of the liquidated damages clause.
The contract provided that Ingram Corporation would construct additions to the treatment facilities at Stickney and an unloading dock and pump station in Fulton County, for which work the Sanitary District was to pay $733,000. Ingram Corporation was also to construct a pipeline over property not owned by the District, for which construction the District agreed to pay $68,000 per month for 36 months, a total of $2,448,000. The contract also provided that Ingram Corporation would receive $1.802 per ton of sludge hauled from Stickney to Fulton County. The parties estimated that over the life of the contract 8,000,000 tons of sludge would be transported.
On May 19, 1971, Weber and Benton met in New Orleans to discuss ways of increasing Ingram Corporation’s total revenue under the contract to the $21,500,000 that McPartlin had assured Benton would be forthcoming. Weber told Benton that Janicki and he thought that the corporation could receive an additional $2,100,000 by billing the Sanitary District a second time for the construction of the pipeline and the construction in Fulton County.
On June 26,1971, Weber told Benton that Janicki needed $21,250 to pay off three District staff members. Ingram issued a check for that amount to Southwest Expressway, another of Weber’s defunct corporations.
On July 27, 1971, Weber issued a $20,000 check to Bull Towing Company. Edwin Bull deposited the check and, at the same time, withdrew $20,000. The next day, the Illinois Commerce Commission granted Ingram Corporation’s request for a certificate of convenience and necessity.
On August 14,1971, Edwin Bull negotiated two contracts with Ingram Corporation. In one of them Ingram Corporation agreed to rent barges from Bull Towing Company to transport sludge from the Lemont Bridge over the Illinois River to Fulton County. Donnelly signed this contract but refused to sign the other contract, under which Ingram Corporation would agree to pay Bull $.17 per ton for transporting sludge from Stickney to the Lemont Bridge. Ten cents per ton were intended as payment for actual towing services; the other seven cents per ton were intended as payment for consulting services and engineering and feasibility studies that Bull had allegedly performed for Ingram Corporation. The second contract also provided for payment to Bull of a $76,000 “finder’s fee.”5 Donnelly objected to the “finder’s fee,” questioned whether any consulting services or studies that Bull provided to Ingram Corporation were worth $560,000, and questioned Bull’s competence as a barge operator. Out of Bull’s presence, Benton told Donnelly that if Bull did not participate in the sludge-hauling contract, there would be no contract. Donnelly still refused to sign the second Ingram-Bull contract, but permitted Benton to sign it on behalf of Ingram Barge Corporation as well as Ingram Corporation.
On August 15, 1971, Benton, Weber, and McPartlin met in Chicago to discuss further payments. Benton agreed to provide $146,-000 in two installments. On August 18, 1971, Oscar Hardison, comptroller of Ingram Corporation, delivered $30,000 in cash to Weber at O’Hare Airport in Chicago. On August 28, 1971, another Ingram executive, G. Glen Martin, gave Weber $116,000, which [1331]*1331consisted of $46,000 in cash and $70,000 in checks payable to Weber’s defunct corporations.
Ingram Barge Corporation began transporting sludge six days later than the date it was required to do so under the sludge-hauling contract; whereupon the Sanitary District assessed liquidated damages of $30,000 under the liquidated damages clause. In early October, 1971, Benton, Weber, and Janicki held a meeting in Chicago to discuss this matter, following which the Sanitary District withdrew the assessment. After the meeting, Weber told Benton that Janicki wanted $100,000 by the end of 1971. When informed by Benton of this request, however, Frederick Ingram refused, saying that no more payments would be made until the Sanitary District began making payments on the pipeline, as Weber had promised it would.
On December 15, 1971, Weber telephoned Benton to tell him that the Sanitary District would issue a check to Ingram Corporation for $1,000,000, as partial payment on the pipeline. When Benton arrived at Janicki’s office the following day, however, Janicki disclaimed any knowledge of the $1,000,000 check. Benton threatened to “jerk the rug” from under everyone in Chicago.
Upon learning of Benton’s threat, Weber informed Oberle of it and asked Oberle to do whatever he could about Benton. Oberle telephoned defendant Frederick Ingram to tell him of Benton’s threat. Ingram expressed no surprise, simply thanked Oberle for the information and hung up, and later in the day met with Benton to discuss the matter. At the meeting they agreed that Benton would continue to represent Ingram’s interest in dealing with the Chicago officials.
On December 21, 1971, Weber, Janicki, and Benton met in Benton’s hotel room in Chicago. Benton apologized for his threat. He then gave Weber two checks payable to Weber’s defunct corporations in the amount of $50,070. This payment brought Ingram’s total contribution to $317,320, leaving a balance of $132,680 on the $450,000 commitment.
In February, 1972, Weber told Benton that because of the difficulties in getting the Sanitary District to pay the additional $2,100,000 for the pipeline, Ingram Corporation would have to increase its contribution to $620,000. On February 17, 1972, Weber asked Benton for $100,000 in cash immediately. When Benton told defendant Ingram of the request, Ingram responded that he would investigate ways of raising the money. On February 28, 1972, Benton delivered $100,000 to Mrs. Valentine Janicki.
At trial, defendant Frederick Ingram contended that he did not learn until this February, 1972 meeting with Benton that his company had secured a multi-million dollar contract by paying more than $300,-000 to Chicago officials.6 Ingram testified that he protested against paying the bribes, but reluctantly agreed when Benton informed him that if he refused to pay, the Sanitary District would not pay the additional $2,100,000 for the pipeline and would use the liquidated damages clause to penalize Ingram Corporation.
On March 10, 1972, Weber told Benton that if Ingram Corporation could deliver $100,000 before the end of the month, the Sanitary District Board of Trustees would approve the purchase of the pipeline. One-fourth of this amount was delivered, but the balance was not, and the trustees failed to approve the purchase. At a July 6, 1972 meeting between Benton, Janicki, and Weber, however, Janicki promised that the trustees would take some action on the pipeline in the month of July. As promised, the board of trustees authorized the staff to negotiate with Ingram for the purchase of the pipeline on July 20, 1972.
On August 23,1972, Benton gave McPartlin $80,000 in cash. McPartlin told Benton that the trustees would approve the pur[1332]*1332chase of the pipeline in September, but Ingram would have to pay the balance of its contribution, about $95,000, in September also.
Between August and November, 1972, Ingram Corporation and the Chicago officials negotiated a new agreement. Ingram would pay $750,000 over a three year period, and the Sanitary District would purchase the pipeline, modify the liquidated damages clause, and extend the sludge-hauling contract for three years at a higher price per ton.
On December 28, 1972, representatives of the Ingram companies and the District signed an agreement covering the pipeline purchase that was to be effective only if the parties also signed two other agreements: a retroactive modification of the liquidated damages clause and a three year extension of the sludge-hauling contract. On January 26, 1973, the additional agreements were signed.
After the signing, Benton returned to his hotel room and telephoned Janicki to tell him that his money was ready. Janicki sent his secretary to pick up a package containing $50,000 in cash. Benton then telephoned Weber to tell him to come and pick up the balance of the money due. When Weber arrived, Benton gave him $95,000 in cash and nine letters of credit drawn on a Swiss bank in the amount of $70,000 each.7
One of the letters of credit matured in June, 1973, and each of the others matured sequentially at six-month intervals. Weber admitted negotiating the first four letters at the Swiss bank in July, 1973, December, 1973, June, 1974, and December, 1974. On each occasion, he purchased his plane ticket to Europe with cash, arranged for his trip to Switzerland only after he arrived in Europe, and stopped in Toronto, Canada, on the way back to the United States. On his last two trips, Weber telephoned Janicki from Europe.
Sometime before the fall of 1974 a federal grand jury commenced an investigation of the events surrounding the sludge-hauling contract. In May, 1975, the government granted immunity to Benton.
In November, 1975, Weber sent his brother, Henry Weber, to Europe to negotiate the fifth and sixth letters of credit, which matured in June, 1975, and December, 1975.8 Following his brother’s instructions, Henry Weber did not proceed directly to the drawee Swiss bank but went to a bank in Vaduz, Liechtenstein, to have that bank present the letters to the Swiss bank.
On November 26, 1975, two weeks after his return from Liechtenstein, Henry Weber appeared before the grand jury and testified that he had only visited Frankfurt and Munich. On December 3, 1975, the government called Henry Weber to appear a second time before the grand jury, this time asking Weber to bring his travel records. During his second appearance, Henry Weber testified that he had been mistaken when he said that he had only visited Frankfurt and Munich and that he had also visited Vaduz.
On December 9, 1975, Franklin Weber’s attorney telephoned one of the government’s attorneys in this case and informed him of what the government attorney already had reason to suspect, namely, that Franklin Weber had possession of the remaining letters of credit.
Additional details and procedural matters necessary to an understanding of the various issues to be decided will be stated at appropriate places in the opinion.
I.
Severance
Before discussing the specific attacks on the district court’s denial of sever[1333]*1333anee, some general principles should be noted. The question of whether charges that have been properly joined ought to be severed for trial is for the discretion of the trial judge, whose decision will be reversed only upon a showing of clear abuse. United States v. Tanner, 471 F.2d 128, 137 (7th Cir.), cert. denied, 409 U.S. 949, 93 S.Ct. 269, 34 L.Ed.2d 220 (1972). The defendant has the burden of showing prejudice, which is a difficult one. Id. A denial of severance will rarely be reversed on review, Tillman v. United States, 406 F.2d 930, 935 (5th Cir.), cert. denied, 395 U.S. 830, 89 S.Ct. 2143, 23 L.Ed.2d 742 (1969), and then only for the most “cogent reasons,” United States v. Kahn, 381 F.2d 824, 838 (7th Cir.), cert. denied, 389 U.S. 1015, 88 S.Ct. 591, 19 L.Ed.2d 661 (1967). There is, moreover, a strong policy in favor of joint trial “where the charge against all the defendants may be proved by the same evidence and results from the same series of acts.” United States v. Cohen, 124 F.2d 164, 165 (2d Cir.), cert. denied sub nom. Bernstein v. United States, 315 U.S. 811, 62 S.Ct. 796, 86 L.Ed. 1210 (1942). See also United States v. Echeles, 352 F.2d 892, 896 (7th Cir. 1965) recently quoted in United States v. Harris, 542 F.2d 1283, 1312 (7th Cir.), cert. denied, 430 U.S. 934, 97 S.Ct. 1558, 51 L.Ed.2d 779 (1976).
In the case at bar all appellants assert error in the denial of their motions for severance. Frederick Ingram argues that the denial deprived him of evidence that would otherwise have been available. The other appellants, whom we shall call the Illinois defendants, argue that they were prejudiced by the denial because Ingram and his brother (whom the jury acquitted) defended on a ground antagonistic to the defenses of their co-defendants and because of curtailment of cross-examination and the spillover effect of evidence admitted only against Frederick Ingram. We turn first to the argument of the Illinois defendants.
A. The Illinois Defendants
1. Antagonistic Defenses
The Ingrams contended that the payments were made only because the Sanitary District threatened to take action that would have resulted in financial disaster to Ingram Corporation, and therefore neither of them had the “intent (to influence the performance of an official act) required by the Illinois bribery statute.” United States v. Peskin, 527 F.2d 71, 84 (7th Cir. 1975), cert. denied, 429 U.S. 818, 97 S.Ct. 63, 50 L.Ed.2d 79 (1976). It was not necessary to this defense that the Illinois defendants were guilty of extortion or received bribes, because it was possible that Benton, through whom the corporation’s communications with, and payments to, the Illinois defendants were carried out, did not pass any of the money on but kept it all himself.9 Thus the Ingram defense was not necessarily antagonistic to the defenses of others, although it was possible, on the Ingrams’ theory, that they were innocent even if the others were guilty.
Even if the defenses were to a degree antagonistic, however, it does not follow that there should have been two or more trials. One has no right to any tactical advantage that would result if evidence that is admissible against him in either a joint or separate trial might be unavailable in a separate trial. Cf. Brady v. Maryland, 373 U.S. 89, 90-91, 83 S.Ct. 1194, 10 L.Ed.2d 215 (1963).10 It is therefore the settled rule [1334]*1334that a defendant is not entitled to a severance merely because it would give him a better chance of acquittal. See United States v. Tanner, supra, 471 F.2d at 137. Thus antagonistic defenses do not require the granting of severance, United States v. Hutul, 416 F.2d 607, 620 (7th Cir.), cert. denied, 396 U.S. 1007, 90 S.Ct. 573, 24 L.Ed.2d 504 (1970), even when one defendant takes the stand and blames his co-defendant for the crime, United States v. Joyce, 499 F.2d 9, 21 (7th Cir.), cert. denied, 419 U.S. 1031, 95 S.Ct. 512, 42 L.Ed.2d 306 (1974). Even when the defendant who testified he was the victim of extortion had dealt directly with the defendant alleged to have extorted the bribe, we sustained the denial of severance. United States v. George, 477 F.2d 508 (7th Cir.), cert. denied, 414 U.S. 827, 94 S.Ct. 49, 38 L.Ed.2d 61 (1973).
There may be cases, as we recognized in George, in which the conflict among defendants is of such a nature that the “jury will unjustifiably infer that this conflict alone demonstrates that both are guilty.” 477 F.2d at 515. This is not such a case. The joinder did not result in the exclusion or admission of any evidence of consequence that would not have been ex-cludable or admissible in separate trials. Nor was any argument made that could not properly have been made in such a separate trial. There was no cognizable prejudice arising from antagonistic defenses.11
2. Curtailment of Cross-Examination
Janicki complains that cross-examination was curtailed because of the joinder when, during cross-examination of Benton, the trial judge delivered a general admonition against repetitious cross-examination. Neither Janicki nor the other Illinois defendants, who adopt by reference his arguments on severance, show any prejudice resulting from the admonition or point to any specific ruling curtailing their cross-examination. It was, moreover, entirely proper for the judge to attempt to forestall repetition.
3. Spillover Effect of Evidence Offered Against Frederick Ingram
Janicki also asserts that he was prejudiced by evidence offered against Frederick Ingram showing that Ingram Corporation had bribed a Brazilian corporate official between 1969 and 1971, because the conduct of the Brazilian was similar to that with which Janicki was charged. The trial court instructed the jury to consider the evidence of the earlier bribe only as to Frederick Ingram’s state of mind, but Janicki asserts that this instruction was ineffective. We see no substantial risk that the jury would believe that because a Brazilian corporate officer took a bribe from Ingram Corporation, Janicki did also, and therefore we conclude that Janicki was not prejudiced by the admission of this evidence. Its admissibility as to Frederick Ingram and the effectiveness of the limiting instruction are discussed below.
[1335]*1335The Illinois defendants were not deprived of a fair trial by the joinder.
B. Frederick Ingram
Frederick Ingram’s attack on the joinder is based on the district court’s exclusion of three items of evidence offered to support his extortion defense, which Ingram argues occurred because he was tried with the men he allegedly bribed.
1. The McPartlin Statements and the Attorney-Client Privilege Among Co-defendants and Their Counsel
Throughout the period covered by the indictment, Benton kept diaries, or appointment calendars, in which he made notes concerning meetings and telephone conversations, naming the persons involved and often recording the substance of the conversations. The Benton diaries figured prominently in the government’s case, for they corroborated much of his testimony.
Destroying Benton’s credibility was important to Ingram, as it was to the other defendants, even though Ingram’s defense was based, in part, on the argument that he had made, the payments in response to the threats Benton had reported to him, because Ingram’s account of events in issue differed materially from Benton’s, and because the government’s case hinged largely on Benton’s testimony. Since Benton’s diaries corroborated so much of his testimony, it was imperative from the standpoint of all defendants that an effort be made to discredit them.
Such an effort was made, and Frederick Ingram and McPartlin cooperated in that effort. In a brief supporting a pretrial “Motion for Additional Time to Conduct Document Analysis,” Ingram’s counsel stated, with reference to contemplated tests on the Benton diaries,
[Tjhe defendant Frederic B. Ingram is not the only defendant who may be affected by the results of these tests. Besides the general effect of the doubts that may be raised as to Benton’s veracity and the credibility of the diary entries, the case against at least one other defendant — Robert F. McPartlin — may be substantially affected by the results of the tests. From the results of the tests conducted so far, it appears that at least two of the suspicious diary entries relate to alleged payments of money to Mr. McPartlin.
An investigator acting for Frederick Ingram’s counsel twice interviewed McPartlin with the consent of the latter’s counsel12 for the purpose of determining whether there was a basis for challenging the truth of some of the diary entries. In the second of these interviews McPartlin made certain statements, which Ingram argues tend to support his defense. At trial, when Ingram offered evidence of these statements, McPartlin’s counsel objected on the ground, inter alia, of the attorney-client privilege, and the court, after an in camera hearing, sustained the objection on this and another ground.13
The exclusion of the McPartlin statements would not be reversible error even if he had not been entitled to claim the privilege. We are satisfied from our examination of the transcript of the in camera hearing, which was sealed and made a part of the record on appeal, that the statements merely corroborated facts which were admitted in evidence and which the jury obviously found to be true.14 We do not disclose [1336]*1336the contents of the statements because they remain protected by the attorney-client privilege, on which we alternatively base our ruling on this point.
McPartlin was entitled to the protection of the attorney-client privilege, because his statements were made in confidence to an attorney for a co-defendant for a common purpose related to both defenses. They were made in connection with the project of attempting to discredit Benton, a project in which Ingram and McPartlin and their attorneys were jointly engaged for the benefit of both defendants. Ingram acknowledges that communications by a client to his own lawyer remain privileged when the lawyer subsequently shares them with co-defendants for purposes of a common defense. The common-defense rule, which is not as narrow as Ingram contends, has been recognized in cases spanning more than a century. Chahoon v. Commonwealth, 62 Va. (21 Gratt.) 822 (1871); Schmitt v. Emery, 211 Minn. 547, 2 N.W.2d 413 (1942); Continental Oil Co. v. United States, 330 F.2d 347 (1964); Hunydee v. United States, 355 F.2d 183 (9th Cir. 1965); Matter of Grand Jury Subpoena, 406 F.Supp. 381, 387-389 (S.D.N.Y.1975); see State v. Emmanuel, 42 Wash.2d 799, 259 P.2d 845, 854-855 (1953); Note, “Waiver of Attorney-Client Privilege on Inter-Attorney Exchange of Information,” 63 Yale L.J. 1030 (1954); Note, “The Attorney-Client Privilege in Multiple Party Situations,” 8 Colum.J.L. & Soc.Prob. 179 (1972). Uninhibited communication among joint parties and their counsel about matters of common concern is often important to the protection of their interests. Note, supra, 8 Colum. J.L. & Soc.Prob. at 179 — 180. In criminal cases it can be necessary to a fair opportunity to defend. Therefore, waiver is not to be inferred from the disclosure in confidence to a co-party’s attorney for a common purpose.
In the case at bar, the judge found, as a preliminary question of fact, from the evidence adduced at the hearing held pursuant to Rule 404(a), Fed.R.Evid., that McPartlin had made the statements to the investigator in confidence. That finding is not clearly erroneous.
Ingram argues that the co-defendants’ defenses must be in all respects compatible if the joint-defense privilege is to be applicable. The cases do not establish such a limitation,15 and there is no reason to impose it. Rule 503(b)(3) of the proposed Federal Rules of Evidence, as approved by the Supreme Court, stated that the privilege applies to communications by a client “to a lawyer representing another in a matter of common interest.” See 2 J. Weinstein, Evidence 503-52 (1977). The Advisory Committee’s Note to proposed Rule 503(b) makes it clear that the joint-interest privilege is not limited to situations in which the positions of the parties are compatible in all respects:
The third type of communication occurs in the “joint defense” or “pooled information” situation, where different lawyers represent clients who have some interests in common. . . . The rule does not apply to situations where there is no common interest to be promoted by a joint consultation, and the parties meet on a purely adversary basis.
Quoted in 2 J. Weinstein, supra, at 503-6 to 503-7. (Emphasis supplied and citations omitted.) Although the Congress, in its revision of the Federal Rules of Evidence, deleted the detailed privilege rules and left the subject of privilege in federal question [1337]*1337cases to “be governed by the principles of common law as they may be interpreted by the courts of the United States,” R. 501 Fed.R.Evid., the recommendations of the Advisory Committee, approved by the Supreme Court, are a useful guide to the federal courts in their development of a common law of evidence. 2 J. Weinstein, supra, at 501-20.4 to 501-20.5. In this instance we follow the recommendation. The privilege protects pooling of information for any defense purpose common to the participating defendants. Cooperation between defendants in such circumstances is often not only in their own best interests but serves to expedite the trial or, as in the case at bar, the trial preparation.16
Ingram also seems to argue that the communication was not privileged because it was made to an investigator rather than an attorney. The investigator was an agent for Ingram’s attorney, however, so it is as if the communication was to the attorney himself. “It has never been questioned that the privilege protects communications to the attorney’s . . . agents . for rendering his services.” 8 Wigmore, Evidence § 2301 at 583 (McNaughton rev. 1961); cf. United States v. Kovel, 296 F.2d 918, 921-922 (2d Cir. 1961) (client's communications to an accountant employed by his attorney).
Nor was it, as Ingram contends, fatal to the privilege that McPartlin made the statement, in effect, to Ingram’s attorney rather than his own. When the Ingram and McPartlin camps decided to join in an attempt to discredit Benton, the attorney for each represented both for purposes of that joint effort. The relationship was no different than it would have been if during the trial the Ingram and McPartlin attorneys had decided that Ingram’s attorney would cross-examine Benton on behalf of both, and during cross-examination McPartlin passed Ingram’s attorney a note containing information for use in the cross-examination. The attorney who thus undertakes to serve his client’s co-defendant for a limited purpose becomes the co-defendant’s attorney for that purpose. A claim of privilege was upheld in circumstances such as these where communications were made directly to the attorney for another party in In the Matter of Grand Jury Subpoena Duces Tecum, supra, 406 F.Supp. at 391. United States v. Friedman, 445 F.2d 1076, 1085 n.4 (9th Cir.), cert. denied, 404 U.S. 958, 92 S.Ct. 326, 30 L.Ed.2d 275 (1971), relied on by Ingram, is not to the contrary. In Friedman the court held its decision in Hunydee v. United States, supra, inapplicable, because no joint defense or common interest was alleged. The court went on to state, in the footnote relied upon, that even if Hunydee was applicable, there was no privilege since “the facts of the conversation negate confidentiality.” 445 F.2d at 1085 n.4.
Inasmuch as McPartlin was entitled to assert the privilege whether Ingram was tried jointly or separately, no prejudice would have resulted from the joint trial by reason of the exclusion of the McPartlin statements even if those statements had not been merely cumulative.
2. Relevance of Threats Against Benton
Frederick Ingram also argues that joinder caused specific prejudice through the trial court’s exclusion, as prejudicial to other defendants, of evidence of threats of physical harm directed against Benton. The short answer is that prejudice to other defendants was not the only ground for the exclusion. The excluded evidence consisted of testimony by Ingram that in the fall of 1972 Benton expressed fear for his own physical well-being if Ingram refused to make the promised payments to the Chicago officials, and testimony by two other witnesses that Benton told them in October 1974 that someone had threatened him with physical harm. To begin with, both state[1338]*1338ments by Benton were said to have been made long after February 1972, when Ingram, by his own admission, authorized Benton to make payments to secure the contract. There is no indication in the record that the second, made long after all payments were made was ever communicated to Ingram. The alleged threats were directed at Benton, not Frederick Ingram, who had no dealings in the matter with anyone outside Ingram Corporation. Finally, Ingram’s theory throughout the trial was economic, not physical, coercion.17 The evidence was properly excluded as irrelevant, and it would have been equally irrelevant if Ingram had been tried separately.
3. Relevance of an Unrelated Payment by a Third-Party
Frederick Ingram also contends that the joinder caused the exclusion of evidence that an attorney who represented Ingram Corporation before the Illinois Commerce Commission made a $5,000 contribution to McPartlin’s reelection campaign fund, and that the payment was motivated in part by McPartlin’s having recommended the attorney’s firm to Ingram Corporation. There was no showing that the attorney was coerced. This evidence, offered first by the prosecution and then by the Ingrams, was rightly excluded on both occasions as irrelevant. In rejecting the Ingram offer the court said that it “could be prejudicial to McPartlin without being probative of any issue as far as the Ingrams are concerned.” Prejudice to McPartlin aside, the trial court was correct as to the probative value of the evidence.
We therefore conclude that the denial of the motions for severance was not error.