To have one conspiracy theory in full flow is a misfortune. To have two going at the same time is surely absurd. And yet, for anyone attempting to make sense of the case of the Libyan bomber, there is a further troubling problem.

In order to dismiss both conspiracies out of hand, you have to believe in a quite remarkable coincidence: that, separately, with no conferring and with no collusion, the SNP administration in Scotland succeeded in reaching the very goal that the British Government had been so keen to achieve — to have Abdul Baset Ali al-Megrahi returned to Libya, thus removing the one obstacle that lay between the UK and a lucrative oil and trade deal.

The papers published yesterday on the release of the Libyan do nothing to undermine the scenario, of which two justice ministers north and south of the border are anxious to convince us: that his release, on compassionate grounds, had nothing whatsoever to do with the deals that the UK Government had been pursuing. As Jack Straw, in London, so earnestly explains, the matter was entirely in the hands of his opposite number in Scotland. As Kenny MacAskill in Edinburgh, with equal vigour, reiterates, nothing that London was doing had any impact whatsoever on his decision to allow al-Megrahi home to die.

Thus far, there is nothing to disprove their separate assertions. Among the raft of papers we saw yesterday there is no single letter, memo or written agreement to suggest that they were operating in concert. For all the allegations of an unholy network that appears to have included billionaire businessmen, Colonel Gaddafi’s son and Lord Mandelson — whose very involvement adds a whiff of conspiracy — nothing has emerged to show that the Scottish government was caving in to pressure to release al-Megrahi.

Indeed, the very suggestion that the First Minister of Scotland, Alex Salmond, whose entire stock in trade lies in his resolute independence, might have been part of a grubby deal to repatriate a known terrorist in order to oil the wheels of a London-inspired trade deal is surely nonsense.

And so we must accept that, must we not? For those of us who detest the very phrase “conspiracy theory”, the lack so far of a smoking gun to prove collusion is tantamount to demonstrating that one does not exist. Yet each time we proclaim it, another smidgin of evidence emerges to plant a seed of doubt, and to demand further explanation.

The latest came yesterday, among the documents released by the Scottish government. One of them has Bill Rammell, a Foreign Office minister, visiting Libya in March this year and assuring the Libyans that neither Gordon Brown nor his Foreign Secretary wanted al-Megrahi to die in a Scottish prison. Nothing wrong with that: it was an expression of opinion. Two months later, in May, a prisoner transfer agreement, which now includes al-Megrahi, is ratified. Nothing startling about that — it was in the pipeline. Two months after that, Ivan Lewis, a Foreign Office minister, tells the Scottish government that he hopes Mr MacAskill will now consider the prisoner transfer request. Nothing dubious here — we know that the UK Government wants the trade deal to go through, and the Libyans have made it clear that al-Megrahi is the outstanding obstacle to that.

In Scotland, meanwhile, demonstrating his robust independence, Mr MacAskill rules out any suggestion of a prisoner transfer and assures the relatives of US victims that the Libyan will not be released under this agreement. Within a month, however, he has visited al-Megrahi in his cell in Greenock jail to assess his application for release on compassionate grounds. He finds that he is indeed seriously ill and confirms that the judicial system allows him to release any prisoner with less than three months to live.

Within days, the process has speeded up. The Libyan applies to the Scottish courts to drop his appeal, the BBC broadcasts that he is to be released on compassionate grounds and, just over a week later, Mr MacAskill formally confirms the fact. Soon afterwards, al-Megrahi is on his way home.

No smoking gun, no conclusive evidence. Those of us who believe in proof as an essential ingredient of good journalism cannot close the gap, however tempting that may be. But there is a host of questions demanding answers. Here are a few.

Why was the Scottish government so hell-bent on releasing al-Megrahi? Was it motivated solely by humanitarian considerations or were it anxious, like its UK counterparts, to keep on good terms with the Libyans?

Why did al-Megrahi, who had always proclaimed his innocence, suddenly decide to drop his appeal against conviction when there was no need? Was he lent on by the Libyans, who wanted to bury further evidence, or indeed by the Scots, worried that the outcome might embarrass the judicial system?

Why did Mr MacAskill reject the opportunity of allowing al-Megrahi to die in a Scottish hospital, where the interests of justice and compassion would have been jointly served? Why, in short, was the drive to return al-Megrahi put before all other considerations — judicial, political, dipomatic?

To ask these questions is not to aid the conspiracy theorists. It is to demand the wideranging judicial inquiry that this affair now requires.

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