MOORE, Circuit Judge:
International Business Machines Corporation (IBM) is the defendant in an antitrust1 action brought by the United States of America (the Government) in the United States District Court for the Southern District of New York (the New York action). Also pending against IBM are a number of private antitrust actions which have been consolidated in the United States District Court for the District of Minnesota before Judge Phillip Neville. These actions may be referred to as Control Data Corp. v. International Business Machines Corp.2 or, for brevity, the CDC action. The Government is not a party to the actions in Minnesota but has attended various depositions and has received the cooperation of counsel there. In short, it is not a complete stranger to those proceedings.
The present appeal and Petition for Extraordinary Writ (28 U.S.C. § 1651; Fed.R.App.P. 21) are addressed to an order in the New York action (Pretrial Order No. 5) made by Chief Judge Edelstein on September 26, 1972, wherein he, after a preamble reciting that IBM “in furnishing to plaintiff, United States of America, microfilm copies of documents in the course of pretrial proceedings * * * excised from the microfilm prior to delivering it to plaintiff copies of documents reproduced on said microfilm which constituted or contained allegedly privileged material, as to which excised documents IBM made the claim that such documents had been delivered to a third party, Control Data Corporation, through inadvertence on its part;” and that the Government “filed a motion in this Court dated April 7, 1972, calling for the production of the materials thus withheld and excised by IBM, plaintiff’s ground being that the production of said documents to Control Data Corporation constitutes a waiver of all claims of privilege by IBM as to said documents”, entered an order directing that “IBM immediately deliver to plaintiff, in the form provided to Control Data Corporation, a copy of each document withheld and excised by it from the said microfilm, all such documents purportedly being identified and described by Charles M. Waygood, attorney for defendant, in a letter addressed to plaintiff’s counsel, dated April 4, 1972, a copy of said letter being attached to and made a part of this order.”
IBM requests that this Court vacate Pretrial Order No. 5 on the ground that, in producing the documents to Control Data under compulsion of discovery orders issued by the Minnesota district court, which orders expressly protected the right of privilege in the documents, IBM cannot, as the Government argued in its motion below, be held to have waived privilege in the documents in the New York action.
I.
The issues presented in this appeal derive from a decision made by the Government, in effect, to abandon its own, independent discovery program in the New York action and instead to participate in the documentary discovery program already underway between IBM and Control Data in the Minnesota action. Recognizing that “the parties in the [Minnesota] private suit were substantially ahead of us” and that partici[509]*509pation in the discovery there would be “of tremendous help to the Government in trying to reach a point of knowledge of its case where it can move ahead as rapidly as we think that it should be moved ahead,” 3 the Government elected to terminate its review of IBM documents and to accept copies of the documents IBM supplied to Control Data. Two alternatives for obtaining microfilm copies of the documents delivered to Control Data were proposed:
1. under the first alternative, “IBM would deliver all the documents selected by CDC [Control Data Corporation] (whether or not privileged) and the Government would stipulate that IBM had not waived any privilege claims as to any of the documents”;
2. under the second alternative, “IBM would first edit from the CDC microfilm [already delivered to CDC] documents for which privilege was claimed, and then supply the Government with a list showing the author, addressee, nature of privilege, date, file source and copyee for every document removed from the microfilm.” 4
The parties agreed on the second proposal, an agreement which the Government subsequently challenged on the ground that IBM was acting in bad faith by editing from the microfilm it had delivered to CDC an unreasonable quantity of material before turning it over to the Government. The Government therefore moved Judge Edelstein on April 7, 1972, to order IBM to produce the materials excised and withheld by IBM, arguing that the production of the documents to CDC constituted waiver of all claims of privilege in those documents, and that, because they were now “in the public domain”, the documents should be made available to the Government. The granting of the Government’s motion is embodied in Pretrial Order No. 5.
Since no specific document is before us, we must assume that the contents of the some 1,200 documents in question fall within the attorney-client privilege —a privilege which the courts throughout the centuries have zealously protected.5 Therefore, if the order in the New York action merely directed IBM in substance to produce all letters between IBM and its attorneys with the explanation that the Court did not believe in the attorney-client privilege and, therefore, chose not to honor it, we might well have before us a situation in which this Court should intervene at this stage to prevent irreparable injury. But this is a hypothesis which, having raised it, we can ignore because undoubtedly Judge Edelstein never would have issued such an order and did not. The practical effect of Pretrial Order No. 5, however, is just as surely to deprive IBM of the right to assert the attorney-client and work-product privileges in the New York action, or to assert the non-waiver thereof. Because Judge Edelstein did not write an opinion to accompany the order, nor make any findings of fact, the rationale underlying his discovery order is not evident.
Although the Government is not a party in the Minnesota action, Pretrial Order No. 5 is inextricably tied into that action because the documents in question are indisputably part of “documents [which] had been delivered to a third party, Control Data Corporation, through inadvertence on [IBM’s] part” and the order provides that “IBM im[510]*510mediately deliver to [the Government], in the form provided to Control Data Corporation, a copy of each document withheld and excised by it from said microfilm, * * The Government does not dispute that the Minnesota district court regulated every facet of IBM’s document production to Control Data, including the volume and speed of production (IBM and CDC were placed on an accelerated schedule of document production), the mechanics of IBM’s review for privileged documents, and the limitations imposed on Control Data’s use of the IBM documents. As already noted, the Government saw many advantages to abandoning its own documentary discovery and to binding itself to the IBM-CDC discovery program, not the least of which was the accelerated schedule imposed by Judge Neville, a schedule which would both facilitate the progress of the New York action as well as avoid duplicative effort and expense.
By order of October 19, 1970, Judge Neville accelerated even further the already massive IBM-CDC document inspection program. The magnitude of the program may be evidenced from the fact that IBM itself copied or microfilmed some 80 million CDC documents and that CDC sent a staff of some 61 persons to IBM offices to inspect and copy documents. The strenuous schedule imposed by Judge Neville caused inevitable problems. IBM discovered that, despite its careful pre-examination of documents for privilege, due to the greatly accelerated schedule ordered by Judge Neville, certain privileged documents were inadvertently falling into Control Data’s possession. To effect a further screening process, IBM placed a lawyer at the document storage room where CDC was microfilming to make a final inspection of the documents selected by CDC for copying and to withdraw any privileged document before CDC copied same. Control Data in turn complained that this “interceptor”, as he was called, seriously impeded the inspection schedule and asked the court to remove him. In the interest of expedition, Judge Neville did remove the interceptor, but on the express condition that he “would thereafter brook no argument that the privilege had been waived [by IBM] merely because the document had been seen by CDC and perhaps copied.”6 Throughout the IBM-CDC discovery program both parties argued that the other side had waived privilege in certain documents, and both alternatively requested of Judge Neville rulings on the question of waiver. The Judge held several hearings and made several rulings, the last of which occurred on April 18, 1972. On that date an order entitled “Order Re Claimed Waiver of Privilege” was entered in the Minnesota action upon motion by IBM “for a definitive ruling on the question of waiver of privilege of documents”. The order contained a recital of the various conferences, between Court and counsel, and the various orders entered in furtherance of the document inspection program by IBM and CDC — in fact, a quite complete history of the inspection and delivery processes which had been and were being adopted. The Court made clear that in removing IBM’s interceptor the Court had specifically conditioned the order by incorporating therein the following provisions:
1. Neither IBM nor CDC shall be deemed to have waived the attorney-client or other privilege as to any document which heretofore has, or if reasonable precautions as in the past are taken hereafter may, come into the possession of any party pending litigation, including the case of Greyhound Computer Corporation v. International Busines Machines Corporation.
2. The determination as to whether a certain document is in fact privileged shall be made by the Master heretofore appointed by this court under the practices and rulings [511]*511heretofore, or that hereafter may be, established.
3. Any document found to be privileged shall not be admissible in evidence at any trial, or hearing nor used in depositions or other discovery proceedings.
It was within the context of the just recited background and Minnesota district court orders that the Government agreed to bind itself to the IBM-CDC discovery program, and within which it successfully moved Judge Edelstein below to rule that, by making delivery to Control Data, IBM had waived all privileges in the documents.
It is clear to us beyond peradventure that the delivery of the documents pursuant to the Minnesota court order did not constitute a waiver by IBM of its attorney-client or work-product privileges. Of the vast amount of material made available to Control Data and the Government, at issue here are only 1,200 documents. The Government and Judge Edelstein have erroneously, we think, treated the situation as though there has been an uncontroverted waiver of privilege and that the only remaining question is whether the waiver was inadvertent. In our opinion such an approach ignores the real issue, namely, are the documents privileged and was there a knowing and voluntary waiver of the privilege. To our knowledge, these questions have not yet been finally determined and they must be. To resolve the status of each of the 1,200 documents as to privilege, someone having the power to make the determination (a judge or special Master) ultimately will have to rule on that status.
II.
The Government asserts that we lack jurisdiction to entertain either an appeal or a Petition for Extraordinary Writ. At the outset we reject the suggestion that an appeal can properly come before us only if some officer of IBM refuses to deliver the 1,200 documents, subjects himself to the consequences of contempt, and appeals from the contempt judgment.7 The law today must be more ingenious, flexible and resourceful in its ability to avoid any such old-fashioned and semi-barbaric procedure. See United States v. Hemphill, 369 F.2d 539, 543 (4th Cir. 1966) where the Court said:
Despite the comparative promptness with which orders for release on bail or stays may be obtained, that is hardly an appropriate or adequate means for obtaining appellate review of a pre-trial order of dubious validity, or one that was clearly erroneous as we hold this one to have been.
See also Covey Oil Co. v. Continental Oil Co., 340 F.2d 993, 996-997 (10th Cir.), cert. denied, 380 U.S. 964, 85 S.Ct. 1110, 14 L.Ed.2d 155 (1965).8 The courts have shown themselves to be aware of the inadequacy of a doctrine of: disclose all now — appeal later. As was stated in Harper & Row Publishers, Inc. v. Decker, 423 F.2d 487, 492 (7th Cir. 1970), aff’d mem. by equally divided [512]*512Court, 400 U.S. 348, 91 S.Ct. 479, 27 L.Ed.2d 433, reh. denied, 401 U.S. 950, 91 S.Ct. 917, 28 L.Ed.2d 234 (1971): “[Appeal after disclosure of the privileged communication is an inadequate remedy * * This principle has for generations supported countless motions to suppress evidence (alleged to have been illegally obtained) because the law recognizes that an appeal from a judgment based upon its use cannot restore the prejudiced party to the position he would have been in had the evidence been excluded.
Upon the hypothesis that a blanket order as broad and sweeping as the order before us ought to receive appellate review before IBM is irrevocably deprived of its right to claim the attorney-client privilege, what procedures are available to us? The Government suggests, in effect, that this Court is powerless to protect IBM against a court-compelled violation of the attorney-client privilege. We do not accede to such helplessness. The argument is then proffered that the Expediting Act (15 U.S.C. § 29) here controls and that it provides an appeal only to the Supreme Court. This statute, however, applies only to final judgments.9 And surely the Supreme Court should not be plagued by anything less. Since Judge Edelstein would not issue the 28 U.S.C. § 1292(b) certificate necessary to prosecute this appeal under § 1292,10 two roads are open to us — both lead to the same destination (appellate review), namely, 28 U.S. C. § 129111 (the so-called Cohen 12 path) and 28 U.S.C. § 165113 (the All Writs path). Under the unique circumstances presented by the facts here, in which the discovery order of a district court in this Circuit is in direct conflict with the discovery order of a district court in the Eighth Circuit, and which conflict not only violates the rights of a private party (IBM) but also disrupts the administration of justice! in the federal court system, both paths suffice to confer the right of review upon this Court.
Review Under 28 U.S.C. § 1291
In Covey Oil Co. v. Continental Oil Co., supra,, the Court stated that “ [t] he threshold question of appealability is not to be decided by rote, [footnote omitted] because cognizance must be given to the competing requirements of finality and fairness to the witness.” (340 F.2d at 996) In that case a non-party witness was called on to disclose trade secrets. The Court stressed “the right to protection from the disclosure of trade secrets” and noted that “[t]he practical effect of the order will' be irreparable by any subsequent appeal.” (Id. at 997) Its conclusion was that the order was appeal-able. However, on the merits the Court allowed the subpoena for the production of documents to stand because the “trade secrets [did] not relate to processes, formulas, or methods but rather to price, cost, and volume of sales of gasoline.” (Id. at 999) In contrast to the situation where “[n]o absolute privilege protects the information sought * * * [513]*513from disclosure in discovery proceedings,” (id.), in the IBM case the claim of privilege should be protected before it is lost through judicial error. The party called upon to produce privileged documents is entitled to a judicial determination as to whether any one or more of such documents falls within the “privilege” category. Certainly the Government as an adverse party is not to usurp the functions of a Court in this respect, nor should the district court sanction the usurpation. Furthermore, in Covey Oil, supra, “reasonable protective measures [were] supplied to minimize the effect on the appellants” (id.), even as here Judge Neville’s order contains protective provisions.
Since Judge Edelstein’s order both relates to Judge Neville’s order and collaterally frustrates its most important provision, namely, that IBM’s right to assert the attorney-client privilege in the documents already delivered to Control Data remains unimpaired, we are faced with a situation that does not fit into the general rule that pretrial discovery orders are not appealable. American Express Warehousing, Ltd. v. Transamerica Ins. Co., 380 F.2d 277, 280-281 (2d Cir. 1967) dealt merely with a more usual question presented by a pretrial discovery order: Did the district court erroneously apply the work-product privilege in ordering disclosure of certain documents? We ruled that this Court lacked jurisdiction to review the order: “We do not think that the mere possibility of erroneous application of the Hickman principle [Hickman v. Taylor, 329 U.S. 495, 67 S.Ct. 385, 91 L.Ed. 451 (1947)] to a given set of documents raises a spectre of such dire consequences that immediate appellate review as of right must follow.” (Id. 380 F.2d at 281). But here we must rule on a set of facts that does raise the spectre of dire consequences, on a question not contemplated in American Express: Does a district judge in one circuit have the power to attack collaterally the discovery order of a district court in another circuit, upon the ground that production under the protective umbrella constituted a general waiver? Stated differently, the question is, specifically: Did Judge Edelstein abuse his discretion in compelling the production of privileged documents which were expressly protected by the discovery orders of Judge Neville?
Under 28 U.S.C. § 1291 an appeal may be taken from any “final” order of a district court. In Gillespie v. United States Steel Corp., 379 U.S. 148, 152-153, 85 S.Ct. 308, 311, 13 L.Ed.2d 199 (1964) the Court held that “the requirement of finality is to be given a ‘practical rather than a technical construction’ ” [citing Cohen v. Beneficial Industrial Loan Corp., 337 U.S. 541, 546, 69 S.Ct. 1221, 93 L.Ed. 1528 (1949) and Brown Shoe Co. v. United States, 370 U.S. 294, 306, 82 S.Ct. 502, 8 L.Ed.2d 510 (1962)], and that, in deciding the question of finality, the most important considerations are the “inconvenience and costs of piecemeal review on the one hand and the danger of denying justice by delay on the other [quoting Dickinson v. Petroleum Conversion Corp., 338 U.S. 507, 511, 70 S.Ct. 322, 94 L.Ed. 299 (1950)]”. In ruling that the order appealed from (order striking a cause of action by administratrix and eliminating reference to recovery for certain family members) was "final” for purposes of § 1291, the Court relied on its holding in Cohen, supra, the case which gave rise to the exception to the general rule that interlocutory orders are not appealable. The effect of the “Cohen rule” is to make final, and thus appealable under § 1291, certain orders that do not fully and finally determine the controversy between the parties. Under Cohen the challenged order or ruling must satisfy three criteria: (1) the order must be a final determination of a claim of right “separable from, and collateral to” rights asserted in the main action; (2) the order must be “too important to be denied review”; and (3) review of the order cannot await final judgment on the merits of the main action because “[w]hen that time comes, it will be too late effectively to review the * * * order and the rights con[514]*514ferred * * * will have been lost, probably irreparably.” 337 U.S. at 546, 69 S.Ct. at 1225. We believe that this appeál meets all three criteria and hold that IBM’s claim on appeal, that in complying with Judge Neville’s order to produce the documents to Control Data it did not waive privilege, clearly presents a right “separable from and collateral to” the merits in the Government's antitrust action. Resolution of the question does not depend upon the antitrust laws, as do the issues raised in the main action; and certain it is that Judge Edelstein’s order presents a final determination of IBM’s rights of privilege in the disputed documents. Moreover, the fact that Judge Edelstein’s order is collateral to the main antitrust action under Cohen also- means, necessarily, that it is “ancillary” to the main action — a characterization which has led the Supreme Court to rule that a matter is properly reviewable by an appellate court notwithstanding the strictures of the Expediting Act. See Shenandoah Valley Broadcasting, Inc. v. ASCAP, 375 U.S. 39, 40-41, 84 S.Ct. 8, 11 L.Ed.2d 8, modified, 375 U.S. 994, 84 S.Ct. 627, 11 L.Ed.2d 467 (1963), relied upon in Garrett Freightlines, Inc. v. United States, 405 U.S. 1035, 92 S.Ct. 1311, 31 L.Ed.2d 577 (1972), which dismissed the appeal in an antitrust case in which the Government was an active participant (United States v. Navajo Freight Lines, Inc., 339 F.Supp. 554, 555 (D.Colo. 1971)). The Supreme Court’s citation of Shenandoah in dismissing Garrett raises the inference that Shenandoah permits a court of appeals review of ancillary matters, without conflict with the Expediting Act, even where the Government is a party to the action. (See note 9, supra.)
The recent (December 6, 1972) decision of the Supreme Court in Tidewater Oil Co. v. United States and Phillips Petroleum Co., 409 U.S. 151, 93 S.Ct. 408, 34 L.Ed.2d 375 (U.S. 1972), dealing with an attempted appeal to the Court of Appeals for the Ninth Circuit which was rejected , by that Court on the ground that it lacked jurisdiction over an appeal in a government civil antitrust case because of § 2 of the Expediting Act, does not bear upon the problem here presented to us by the appeal or the petition for an Extraordinary Writ. In Tidewater Oil, Tidewater Oil, an original party along with Phillips, sought to be dismissed as a party. The district court denied dismissal but certified under 28 U.S.C. § 1292(b) that a “controlling question of law” existed. The appeal to the Court of Appeals was obviously from an interlocutory order — but it was equally obvious that the order was a part of the main action. After tracing the history of the Expediting Act and stressing the purpose of Congress “to speed appellate review by channeling appeals in Expediting Act cases directly to this Court [Supreme Court] and to avoid the delay inherent in piecemeal appeal by conditioning appeal upon the presence of a ‘final judgment’ [footnote omitted]” (409 U.S. at 155, 93 S.Ct. at 412), the Court stated that: “Congress was also intent upon facilitating review by this Court ‘of a class of antitrust cases deemed particularly important’ ”, and that Congress chose to vest exclusive appellate jurisdiction in the Supreme Court “[b]ecause of the importance of uniform interpretation of the antitrust law,” which.would “involve issues of wide importance.” (409 U.S. at 156, 93 S.Ct. at 412). This underlying rationale is found throughout the opinion, namely, that the Act was designed to limit “review of important questions of antitrust law to this Court.” (- U.S. at -, 93 S.Ct. at 417); that the “plain and unaltered intent of Congress [was] to require that appeals in government civil antitrust cases be taken only from final judgments and only to this Court”; and that were “any issue determined on interlocutory appeal [it] would normally be open to consideration on final appeal [footnote omitted]” (409 U.S. at 165, 93 S.Ct. at 420). To make its position even stronger, the Court added: “Of course, nothing we say today signifies a retreat from our previous statements that appeals of [515]*515interlocutory orders in government civil antitrust cases cannot be taken even to this Court.” (409 U.S. at 161, 93 S.Ct. at 415 n. 25) (emphasis in original).
Taken literally the latter pronouncement would mean that, from the moment a complaint is served in a government civil antitrust action, no party defendant, no subpoenaed witness, no stranger to the proceeding called upon to produce privileged papers, or no attorney sought to be questioned as to confidential advice which he gave his client could enter any court house in the country to seek to prevent the invasion of his most personal constitutional rights or a violation of rights well established by law.
We believe that such a reductio ad absurdum result does not emanate from, or is even to be inferred from, the language of the Tidewater Oil decision, the intent of the Court, the wording of the Expediting Act or the intent of Congress.
A single practical illustration should suffice. The custodian of the 1,200 allegedly privileged papers in the instant case disregards (with or without advice of counsel) the order to produce. A contempt order of commitment then issues. The jail door closes. The Supreme Court has said that it will review only the final judgment so that it can pass upon important questions of antitrust law. But the order of incarceration has nothing to do with antitrust law. It is entirely ancillary or collateral to the “mainstream” of the antitrust litigation. The victim has no particular interest in the refinements of that field of the law. All that he desires is some court to which he can appeal the unlawfulness of his confinement. We doubt that the Supreme Court would interpret its Tidewater Oil decision as requiring the contemnor to languish in jail for five or more years with the dubiously cheerful knowledge that due process of law eventually would be accorded him when the antitrust appeal would be finally decided.
Except for the fact that the order to produce was made by a district judge who has the preparation and ultimate trial of an antitrust case under his supervision, the relief sought here by appeal or by Extraordinary Writ is entirely collateral to the issues in the main case. It is even further removed from the principal action than the situation presented in Cohen was from the main case there. It is for this reason that we say the Expediting Act by language and intent does not bear upon the specific problem now before us. To hold otherwise would be to say that no appellate review is ever available to restrain threatened court action no matter how irreparable the damage flowing therefrom. This we are not prepared to say.
If IBM is compelled to obey Judge Edelstein’s order, and to forsake the protection provided by Judge Neville’s order, the harm thus caused IBM cannot effectively be remedied by an “appeal from the final judgment” under the Expediting Act. We can do no better than repeat the words of the Cohen Court, (337 U.S. at 546, 69 S.Ct. at 1225): [516]*516Unquestionably, 28 U.S.C. § 1291 was designed to permit appellate review in a situation such as here presented, where a litigant has been placed on the horns of a dilemma by the conflicting pretrial orders of two district judges.
[515]*515When that time comes, it will be too late effectively to review the present order and the rights conferred by the statute [here by Judge Neville’s order and the law of privilege] * * * will have been lost, probably irreparably.14
[516]*516Review Under 28 U.S.C. § 1651
This Court heretofore has ruled that “When a discovery question is of extraordinary significance or there is extreme need for reversal of the district court’s mandate before the case goes to judgment, there are escape hatches from the finality rule” of 28 U.S.C. § 1291, namely, “a certification by the district court under 28 U.S.C. § 1292(b), * * * or an extraordinary writ” under 28 U.S.C. § 1651.15 American Express, supra, 380 F.2d at 282. In American Express we noted that the touchstones for review by mandamus, as enunciated by the Supreme Court in Schlagenhauf v. Holder, 379 U.S. 104, 110-111, 85 S.Ct. 234, 13 L.Ed.2d 152 (1964), are (1) usurpation of power by the district court, (2) clear abuse of discretion by the district court, or (3) the presence of an issue of first impression.16 Other courts have similarly observed that, in the discretion of the appellate court, mandamus should lie only in exceptional circumstances, where the writ will aid the court’s jurisdiction, or where immediate review is necessary for “proper judicial administration in the federal system.” La Buy v. Howes Leather Co., 352 U.S. 249, 259-260, 77 S.Ct. 309, 315, 1 L.Ed.2d 290 (1957). See also Will v. United States, 389 U.S. 90, 108, 88 S.Ct. 269, 19 L.Ed.2d 305 (1967) (Black, J., concurring); 9 J. Moore, Federal Practice, ¶110.26 (2d ed. 1970). Although as a general rule ordinary discovery orders are not, and should not be, appealable, occasionally there arises a discovery question presenting a question of law capable of general resolution; under such circumstances appellate review by suervisory mandamus provides a logical method by which to supervise the administration of justice within the Circuit. We think the facts here presented fit squarely into that category of situations. Unless we review immediately Judge Edelstein’s order not only will IBM’s rights be irreparably harmed in the New York action, the order may well disrupt the proceedings in the Minnesota action by destroying privilege in documents which the Minnesota court expressly held to be privileged.
Wherein lies Judge Edelstein’s “clear abuse of discretion” or “usurpation of power”? Pretrial Order No. 5 seemingly rests on the supposition that IBM waived its right to invoke privilege in the New York action when it delivered the disputed documents to Control Data in the Minnesota proceedings. Such a supposition clearly ignores the protective provisions of Judge Neville’s “Order Re Claimed Waiver of Privilege”, supra, as well as the intent underlying the contractual agreement between IBM and the Government, supra. When the parties agreed to adopt the “second alternative” by which IBM would supply the [517]*517Government with documents, and when the parties so agreed in light of the Neville order’s protective provisions, it seems to us crystal clear that IBM intended to confer upon the Government rights in the documents no greater than those conferred on Control Data by the Neville order. Insofar as (1) the Edelstein order is in direct conflict with the provisions of the Neville order, (2) the Edelstein order is based on the erroneous assumption that waiver occurred by IBM delivery to GDC, and (3) the Edelstein order has ignored the intent of the IBM-Government agreement, we hold that Pretrial Order No. 5 constitutes a clear abuse of discretion requiring immediate review by extraordinary writ.
In United States v. Hemphill, supra, where the Court concluded that petition for mandamus was an appropriate remedy to review an order to show cause why the Secretary of Labor should not be held in contempt, it was stated:
When a pretrial order is clearly erroneous, an appellate corrective ought to be available if compliance with the order would work a substantial and irreparable deprivation or if the only alternative is submission to a contempt order.
Clearly, mandamus is an appropriate means of reviewing the discovery order before us, and of applying an “appellate corrective” to prevent compelled disclosure of privileged documents. The eases so holding are numerous;17 we point only to a recent representative of the line, Harper & Row Publishers, Inc. v. Decker, supra, 423 F.2d at 492, where the Court, in granting a mandamus compelling the district court to vacate an order permitting plaintiffs to obtain privileged material, noted that the extraordinary remedy of mandamus was appropriate “because maintenance of the attorney-client privilege up to its proper limits has substantial importance to the administration of justice, and because an appeal after disclosure of the privileged communication is an inadequate remedy * * *” (emphasis added). We agree.
Therefore, in our opinion, the two paths converge at a common destination, i.e., appellate review of Pretrial Order No. 5 at this stage of the New York proceedings. Accordingly, we vacate Pretrial Order No. 5 and direct that, with respect to the documents which IBM excised from the microfilm delivered to Control Data, and withheld from the Government in the New York action, said documents containing allegedly privileged material, a new discovery order be entered which provides for a judicial determination of the privileged nature of the documents and for the delivery thereafter to the Government of any documents determined not to be privileged.