Indeed, Aitken is nothing if not cool under fire. In the several scrapes of his surprisingly long career (he grew up politically, after the presidency of the Oxford University Conservative Association, by spending two years as private secretary to Selwyn Lloyd between 1964 and 1966) he has betrayed little, if any, overt sign of strain. And if he thought that there was any danger that he would lose the Cabinet post he finally secured last year at 51, there was no sign.
It is a post he waited a long time for. Asked by Sue Lawley on Desert Island Discs about the 18 years during which he had languished on the backbenches, he replied quite reasonably, but with just a touch of an Eton and Christ Church insouciance that, after all, both Michael Foot and Harold Macmillan had been backbenchers for longer than he had. He did not mention that both had become leaders of their party.
In any case, "languish" is not quite the word. It is true that Margaret Thatcher refused to promote him; whether this was because of the unhappy end to his relationship with Carol Thatcher in the 1970s - the man, in Lady Thatcher's eyes, who "made Carol cry", or whether she had other doubts, has never been clear. She is said to have displayed sometime after her own fall her magnificent contempt for her successor's administration by saying that "only Nicholas Soames and Jonathan Aitken seem to be doing any good and who would have thought that?" What is clear, however, is that a man of substantial intelligence, sharpness and energy (he finished his scholarly, well-reviewed, and largely favourable biography of Richard Nixon while he was a minister) found other channels for his talents while continuing as a far from inactive MP: for example, he ran - it is ironic now to recall - the Euro-sceptic European Reform Group with Sir Teddy Taylor, one of the "whipless" Euro-rebels.
He formed the merchant bank Aitken Hume with his brother Tim in 1981. Although it ran into cash problems early on, by its peak in 1987 it had a market capitalisation of around £100m. Wafic Said, a Saudi international deal-broker on the grand scale, and supposedly a big player in the £20bn Al Yamamah arms and construction contract between British business and the Saudi Royal Family, became a major shareholder. It has subsequently been claimed that Said did so as a personal favour to Mr Aitken, a close friend. Aitken is said to have developed his Arab contacts while representing Slater Walker in the 1970s. By 1989, his listing in the Register of Members' Interests, besides his chairmanship of Aitken Hume, included his directorship of Al Bilad (UK), an investment vehicle for the Saudi Royal Family, and his directorship of TV-am. There was also his directorship of BMARC, the Astra subsidiary at the centre of the current row over the arms deal with Iran. Apart from Wafic Said, one of his closest friends from the Middle Eastern business world is Mohamed Ayas, his fellow director of Al Bilad and his daughter's godfather. He is the man who famously booked his hotel room for a two-day stay at the Paris Ritz while he was already a defence minister in September 1993.
Mr Aitken's eventual explanation - that, despite the presence in the same hotel of Mr Ayas, another Al Bilad director and Mr Said, the trip was a purely social one; and that his bill was partly credited to another account by sheer accident - has been frequently rehearsed. But, broadly, it can be summed up in the memorable terms Aitken's friend Norman Lamont is said to have used (in altogether different circumstances) about the black eye he received in a dispute with an admirer of the society beauty Olga Polizzi - "complicated but innocent".
It would be a gross exaggeration to say that Aitken led a double life in the 1980s. For being a backbencher didn't mean that he wasn't in the political swim. Aitken is one of the few politicians about whom Alan Clark has barely a bad word to utter in his diaries. But Clark does show an insight into Aitken's command of the political black arts. Describing how to take "revenge" on Michael Mates, then chairman of the Defence Select Committee and Thatcher critic, the two men agreed that Aitken should "prime" the Labour MP Tam Dalyell with a parliamentary question about Mates' business relationship with a company doing business with the British Government. And at another point he describes Aitken admiringly, "my old friend and standby for many a dirty trick".
The Chief Secretary is socially liberal, having in the past favoured both the legalisation of cannabis and a much less restrictive official secrets act.
Handsome, rich and glamorous, he is also a sifter of the highest-grade political gossip (he was a percipient political journalist in his youth as well as a brave foreign correspondent), and was an obviously able defence minister. And that is no doubt part of his appeal to his Cabinet colleagues, as well as to John Major. His appointment to the Cabinet last year helped to tilt the Cabinet towards the right. It did more than that: it also helped to provide a counter-weight to Michael Portillo, who enjoys a less cordial relationship with Major than Aitken and is regarded by the Prime Minister as more politically dangerous. His ability to "grasp the point immediately" alluded to in the Clark diaries has been noticeable since he joined the Cabinet; assumed to be a member of the "loyal right", he has given a nudge here and there to policies thought to have the tacit approval of the Prime Minister, from a referendum on Europe to nursery school vouchers and his spate of BBC bashing - which could not go down better among the Tories' core supporters.
But there are also, perhaps, flaws which will in the end stop him going to the top. When he stood trial - and was acquitted - in the late Sixties for breaching the official secrets act by publishing a document highly damaging to the Nigerian cause in the war against Biafra, he emerged as a hero to many journalists for his undoubted courage in the Biafran cause. But there was also a curious sense of relief, reported by some Tory traditionalists at the time in the constituency, that he had to stand down as candidate in Thirsk and Malton. The charge was that he was too metropolitan, too clever by half, too slick.
One close colleague, struggling to describe the impact of last week's fracas over BMARC, referred to the comment in yesterday's Times by its sketchwriter and one time fellow backbencher, Matthew Parris: that after his robust self-defence in the Commons, the Chief Secretary stood there with "the ground firming beneath his feet and the glass ceiling sliding silently into place above his head".Reuse content