Who specifically authorized the worst terrorist outrage ever perpetrated in Britain? Who conceived it? Who built the bomb? And how is it, amid the new controversy over the release of the only man ever convicted in the blast, that investigators never found answers to these most fundamental of questions, and never charged those responsible? The Iran of the early 1990s was considerably more circumspect than it is today about its drive for nuclear weaponry. But it was no less ruthless in the pursuit. And that is why, on August 14, 1993, a very high level group of Iranians, including two cabinet ministers and two military chiefs, sat down together in the city of Mashad to plot their revenge against president Carlos Menem of Argentina, who had had the temerity to scuttle their plans for a rapid march to nuclear self-sufficiency. The mercurial Menem had first suspended, then severed, Argentina's hitherto fruitful partnership with the Iranians on all things nuclear, terminating the training of nuclear technicians in his country and the transfer of nuclear technology to theirs. His perfidy, Teheran decreed, would not go unpunished. Menem's initial suspension of the nuclear partnership at the turn of the 1990s had prompted Iran to commission the 1992 attack on the Israeli Embassy in the Argentinean capital that left 29 people dead. Now the Mashad notables were considering where to strike next, poring over the details of three potential targets supplied by one of their men in Buenos Aires, Mohsen Rabani, who had flown in specially for the consultation. It is not known to this day what the other two potential targets were, because the first location on the list, the AMIA Jewish community headquarters, was quickly approved. Eleven months later, the carefully planned attack was "successfully" executed: a white Renault Trafic van, driven by Lebanese Hizbullah recruit Ibrahim Berro, rammed into the AMIA building, with horrific consequences. The multi-story building collapsed, 85 people were killed and hundreds more were wounded. That we know the specific details of the atrocity's planning, all the way up through the Hizbullah and Iranian hierarchies to the very door of then Iranian president Hashemi Rafsanjani, is thanks to insistent, methodical investigation by the man who for the last five years has been responsible for bringing the AMIA perpetrators to justice, Argentinean prosecutor Alberto Nisman. The AMIA probe initially took all manner of wrong turns. It was almost certainly skewed by Menem himself, who told this reporter days after the blast that he feared for his own life, and was not unreasonably terrified by Teheran's demonstrable viciousness and global reach. It was certainly corrupted by some of Nisman's prosecutorial predecessors, descending for a decade into a farce of bribery and cover-up, and earning condemnation from subsequent Argentinean president Nestor Kirchner as a "national disgrace." But Nisman, defying Iranian death threats and heroically refocusing the probe, two years ago presented sufficient evidence for Interpol to issue arrest warrants for several members of that 1993 Rafsanjani-run, terror-commissioning committee. And so it was that last week, when President Mahmoud Ahmadinejad named Ahmad Vahidi as Iran's new defense minister, the name rang alarm bells and prompted an outcry in Argentina and beyond. For Vahidi, in the early 1990s, was the head of the Quds Force of the Iranian Revolutionary Guards, notorious for its terrorist operations overseas in conjunction with Hizbullah. Vahidi was among the participants in the Mashad meeting. Vahidi, fingered by Nisman, is wanted by Interpol for his role in orchestrating the AMIA bombing. Delighting in his notoriety, and deriding what one lawmaker described as "the Zionist regime's ominous stance against him," the Iranian parliament on Thursday overwhelmingly endorsed Vahidi's appointment. "Iran has always protected terrorists, giving them government posts," observed the unflappable Nisman when news first broke of Ahmadinejad's choice. "But I think never one as high as this one." THE OUTCRY over Vahidi's appointment, indeed the very fact that we know of Vahidi's terrorist activity, underlines the dismal contrast between Argentina's initially flawed and corrupted but ultimately rigorous and unflinching investigation of the AMIA blast and the British-American investigation of the Lockerbie bombing. In short, gutsy Argentina got the job done and did right by the victims of the atrocity it had suffered, and the UK and US, those great, powerful, moralizing democracies, failed. Britain and America are currently embroiled in all manner of controversy and convulsion over the release late last month of the only man ever jailed for the Lockerbie blast, Libyan intelligence agent Abdel Baset al-Megrahi, freed and returned to Col. Muammar Gaddafi's Libya on compassionate grounds as he fights a losing battle with cancer. The AMIA bombing remains the worst terror attack ever perpetrated in Argentinean territory. The Lockerbie bombing, which saw the deaths of all 259 passengers and crew, and 11 people on the ground, when Pan Am Flight 103, en route from London to New York, was blown out of the Scottish skies on December 21, 1988, remains the worst terror attack ever perpetrated in British territory, and killed more American civilians than any single act of terror, with the sole exception of the 9/11 attacks. Argentina, after years of false starts, used insiders' testimonies, followed money trails and employed every other tool at its investigators' disposal to trace the incriminating evidence unwaveringly back to Iran and the specific, top-level individuals who orchestrated the AMIA attack. With the assistance of other nations' investigating authorities, notably Germany's, the British and American authorities probing Lockerbie gave every initial sign of doing the same thing. They recognized an Iranian motive: to avenge the downing, by the US Navy's guided-missile cruiser USS Vincennes, of an Iran Air Airbus in the Persian Gulf five months before Lockerbie, in which all 290 passengers and crew were killed. The US said it had mistaken the civilian airliner for a fighter jet; Iran said the attack was deliberate and vowed revenge; Ayatollah Khomeini promised the skies would "rain blood." They established that the bomb-laden suitcase had come through Frankfurt airport and identified a reportedly Iranian-financed terror cell of the Popular Front for the Liberation of Palestine-General Command, based in Frankfurt, whose members had built and werearrested in possession of bombing devices (hidden in ironically named Toshiba BomBeat radio-cassette recorders) similar to that used to down the Pan Am jumbo jet soon after it set out from Heathrow Airport. But then this Occam's razor of terror trails went bizarrely cold. Suspects slipped through fingers. Alternative theories emerged. And curiously, with the US and UK anxious not to offend the PFLP-GC's Syrian hosts as Damascus joined the coalition against Saddam Hussein in the first Gulf War, and anxious not to spark a complicating confrontation with Iran either, Gaddafi's Libya suddenly emerged as the new prime suspect. Iran, Syria and the PFLP-GC were conveniently off the hook. There were highly credible precedents and motives for Libyan terrorism, too, relating to Libya's various mid-1980s confrontations with the United States - notably Libya's bombing of a Berlin nightclub used by US troops, and American air attacks on targets in Benghazi and Tripoli in 1986, including a strike on the personal quarters of Col. Muammar Gaddafi in which his adopted daughter was killed. But the evidence - well, that was shaky, and not only because it required the bomb to have taken an improbable route from Malta to Frankfurt to Heathrow. Indeed, the evidence was so shaky that even after Gaddafi, battered by financial sanctions, was persuaded to give up two suspects for trial, one of them, Al-Amin Khalifa Fhima, was actually acquitted. And even where the second man, the convicted Megrahi, was concerned, the court acknowledged: "We are aware that in relation to certain aspects of the case there are a number of uncertainties and qualifications. We are also aware that there is a danger that by selecting parts of the evidence which seem to fit together and ignoring parts which might not fit, it is possible to read into a mass of conflicting evidence a pattern or conclusion which is not really justified." MUCH OF the controversy currently surrounding Megrahi's "compassionate" release is focused on allegations that Britain set him free, unconscionably, to facilitate lucrative trade partnerships with Libya. The Americans, led by Secretary of State Hillary Clinton, are publicly outraged. But the other legal and moral consequence of Megrahi's homecoming is that his second appeal against conviction, granted after a four-year investigation by the Scottish Criminal Cases Review Commission, will now never be heard. Megrahi is promising to use some of his little time left on this earth to write an autobiography, in which he will doubtless continue to protest his innocence and set out the grounds on which he had been hoping to prove it at the abrogated appeal. Until then, only his defense team knows how strong a case he might have mounted, but insiders suggest it was formidable. In allowing the appeal, the Scottish review commission suggested several grounds for concern that "a miscarriage of justice may have occurred." Specifically, the insiders say, the defense hoped to demolish the only piece of documentary evidence showing the bomb-laden suitcase to have begun its journey in Malta; to demolish eyewitness evidence that had Megrahi present in a Malta store earlier in December 1988 purchasing the clothing that was packed around the bomb; and to demolish the evidence indicating that only Libya among potential terror states was in possession of the particular timer used in the bomb. These three pieces of evidence were crucial to Megrahi's conviction. With Megrahi having dropped his appeal as the precursor to his release, and although pressure for some kind of independent inquiry into Lockerbie is growing, there is now no prospect of his conviction being tested in a court of law in the light of new evidence - no prospect, that is, of embarrassment for the investigators from the appeal proceedings, no prospect of material emerging in the course of the appeal to bolster the perennial allegations of a miscarriage of justice, no prospect of a renewed hunt for other suspects. In the withering summation of Hans Koechler, who was appointed by the UN Security Council to serve as an observer throughout the Lockerbie legal proceedings, "the search for the truth within the proper judicial framework has been abandoned." IT IS almost unthinkable to suggest that the UK and US would seek to divert a probe into a terror attack of such scale and gravity for the sake of political expediency, however purportedly vital and noble the wider national interest. It is almost unthinkable, furthermore, to suggest that such a diversion could be practically effected - lines of inquiry cobbled, evidence manipulated. Richard Marquise, the 31-year former FBI veteran who led the US task force assigned to the case, has stated emphatically that "there were no conspiracies among the investigators. There was no planted evidence... Prosecutors put together an excellent case." And "I am convinced of the righteousness of [Megrahi's] conviction." Marquise is adamant that "there was never any evidence" of involvement in the Lockerbie affair of the initial key PFLP-GC suspect. He is adamant that the timer used in the bomb had been sold to Libya by its manufacturers. He is adamant that the evidence showing Megrahi to have purchased the clothes packed into the suitcase around the bomb is incontrovertible. But the almost unthinkable suggestions of a miscarriage of justice must be set against the apparent logic of that abandoned initial line of inquiry, with its unerring pointer at a Palestinian terror cell that had the means to carry out such a bombing and the demonstrably vengeful Iranians who had made plain their desire to commission it. They must be set against the inconsistencies and stretched inferences of the original verdict: The judges convicted Megrahi but acquitted Fhima, whom the prosecution had argued was integral to the bombing. The judges wrote that it was not impossible that the timer used in the bomb had come "from some source other than Libya" and that it was not impossible, either, that the bomb-laden suitcase had been "introduced into the airline baggage system at Frankfurt or Heathrow" rather than in Malta. And the judges acknowledged that the Frankfurt-based PFLP-GC cell (whose key members, incidentally, have long been at large in Syria) "had both the means and the intention to manufacture bombs which could be used to destroy civil aircraft" and that its members were found to be in possession of "radio cassette players, explosives, detonators, timers, barometric pressure devices, arms, ammunition and other items, including a number of airline timetables... One of the airline timetables was a Pan Am timetable." The almost unthinkable suggestions of a miscarriage of justice - or worse, a cover-up - must now be set, too, against the fundamental illogic of Megrahi's release: You simply do not set free a man convicted in the deaths of 270 people because he happens to be dying. Perhaps you ease the conditions of his incarceration. But you keep him behind bars until he draws his very last breath. And finally, these almost unthinkable suggestions of a skewed probe and cynically manipulated denouement must be set against another of the abiding mysteries of the Lockerbie investigation - the failure, in such stark contrast to Alberto Nisman's work on the AMIA probe, to vigorously and relentlessly trace the hierarchy of the Lockerbie atrocity all the way up to its senior orchestrators - presumably, if the prosecution case is accepted, Libya's intelligence chiefs and senior officials and, in a one-man regime like Libya's, ultimately Gaddafi himself. A terrorist attack of the complexity of Lockerbie, smuggling a suitcase loaded with an extremely complex bomb through airport security onto a transatlantic flight, was plainly no casual operation. It required immense planning and expertise. Even if Megrahi was indeed a vital cog, that's the most he could have been: a cog. He didn't manufacture the bomb. So who did? He didn't conceive of the operation. So who did? He didn't authorize the operation. So who did? In the AMIA probe, Nisman eventually found answers to all those questions. In the Lockerbie probe, investigators certainly tried for a time - but not relentlessly, not for as long as it took until they could name names, draw up indictments, alert Interpol. Why ever not? Why has the search for all the Lockerbie answers not been maintained to this day? In a short telephone interview from the US on Wednesday, Marquise said Megrahi was no rogue agent, and that Lockerbie could not have been carried out without the knowledge of "the Libyan hierarchy." How far up that hierarchy? All the way to Gaddafi? Given the nature of the tightly controlled Libyan regime, Marquise asked, "If you were a senior minister, would you do this without telling the boss? I doubt it. I have to think [Gaddafi] knew something was going to happen, something that the US would be pissed about, and he said OK." So why, AMIA style, was the investigation not pursued unremittingly all the way to the top? "We couldn't make the connections," said Marquise. "A lot of names came up... We had names of people in the Libyan hierarchy, buying radios, making inquiries about putting bombs in radios... but there was no real overt act [that could serve as the basis for an indictment]." It "would have been nice" to indict the entire Libyan regime, he mused, "but our system wouldn't allow for it. It would have been a real struggle to show Gaddafi and others in the [Lockerbie] chain." Marquise said it had been hoped that Megrahi and Fhima could be arrested before being indicted, and that "they'd give us the whole story, and go up the chain. That didn't happen... And Megrahi never talked. He did everything for his leader." I ASKED Prof. Robert Black, the Scottish lawyer who was the architect of the original trial and who grapples with Lockerbie on a daily, relentless basis, whether he knew of a tireless investigative effort to do for Lockerbie what Nisman has done with AMIA and trace the ostensible Libyan hierarchy of terror. He said he knew of no such effort. And while that might be understandable in today's realpolitik, where Gaddafi is now being rehabilitated, Black noted, it made no sense whatsoever in the years when "mad" Gaddafi's Libya was an international pariah. I asked Black, who was himself born in Lockerbie, whether he had ever seen material evidence purportedly showing where the bomb was assembled, by whom, and who delivered it to Megrahi? For how could Megrahi have been convicted without a chain of evidence tying him to the explosive device itself? "The answer to all of your questions is 'no,' Black replied. "No evidence was led at the trial on any of these matters. And, as far as I am aware, none has subsequently emerged."