The Old Boy angle is not unfamiliar, but it is always fun to read, and Macintyre has some remarkable details. The sheer lack of professionalism is extraordinary. Philby, though with known communist connections from his youth, got into MI6 with only a token vetting, since the deputy head could vouch for him (‘I knew his people’). When his friend Elliott was going through a security check, he was asked if his wife knew he was a spy. Yes, he said, he supposed she had twigged, as she had been his secretary. His mother? ‘Yes, a member of the War Cabinet told her at a party.’ Father? ‘Yes, because the Chief told him in the bar at White’s.’ Later, when Philby – now exposed and living in Moscow – wrote to suggest they might meet and talk about old times in Helsinki or Berlin,Elliott was incensed at his casual advice not to tell his wife, or ‘anybody else, of course’, about the letter: ‘I mean, who the hell did he think I was, not telling them? The first person I’d tell was Elizabeth, and immediately after that, I’d tell Dick White [head of MI6].’

Kim Philby holds a press conference at his mother’s flat in London, November 1955 (photograph by Keystone, Hulton Archive/Getty Images)

That quotation comes from John le Carré, whose twelve-page ‘Afterword’, apparently published here for the first time, is one of the highlights of the book. Le Carré, an MI6 veteran himself, interviewed Elliott in May 1986. Elliott hadn’t much new to say about Philby, but his unwitting insights into the culture of the service are fascinating. About the dénouement in Beirut, le Carré delicately asked if MI6 hadn’t thought of ‘sandbagging’ Philby and bringing him back to London (‘Nobody wanted him in London, old boy’) or even killing him, to which Elliott’s deprecating answer was ‘My dear chap. One of us.’ He gave a similar response when asked why MI6 didn’t contemplate prosecution of Philby, as in the contemporary case of John Vassall, a relatively humble embassy employee who got eighteen years for spying for the Soviets: ‘Ah well, Vassall – well he wasn’t really top league, was he?’

Le Carré and Macintyre both make much of the heavy drinking habits of British intelligence officers, le Carré commenting that ‘alcohol was so much a part of the culture of MI6 in those days that a non-drinker in the ranks could look like a subversive or worse’. Philby and Elliott were both heroic drinkers, with an impressive ability not to reveal any of their secrets, no matter how drunk they were. In general, Philby remained a gentleman under almost all circumstances. His Soviet handler, Yuri Modin, found Philby ‘so completely, psychologically and physically, the British intelligence officer that I could never quite accept that he was one of us, a Marxist in the clandestine service of the Soviet Union’.

It is certainly hard to believe that he was a lifelong Marxist. Macintyre repeats the cliché – Philby’s own line, once he was in the Soviet Union – that he became and remained a spy out of political principle. But there is a welcome note of scepticism: ‘Philby enjoyed deception.’ It would be a rare spy who doesn’t, especially double agents, who are drawn to the risks and excitement of running two professional lives the way others are drawn to cheat on their wives or even run parallel families. Nothing else explains Philby’s voluntary renewal of his Soviet intelligence activities in Beirut, when he could have easily excused himself on the grounds that he was now damaged goods.

Out in the cold: Kim Philby in Moscow (photograph taken from title)

One might wonder if British and American intelligence (with which Philby acted as liaison) would have done better in the postwar years if they had simply done nothing about the Soviet Union, so diligently did Philby pass on their secrets. That, of course, may be the case with intelligence work more often than we think. Ironically, the Soviets underused Philby’s intelligence because, to some KGB analysts, he just looked too good to be true.

Thanks to post-Cold War glasnost, we now have the Soviet side of the Philby story, including a charming Russian biography (N.M. Dolgopolov, Kim Filbi [2011], not used by Macintyre). The author, evidently an ex-KGB man, draws on interviews with Philby’s agreeable Soviet fourth wife, Rufina. His years with her, including visits from his English children and holidays in the sun, seem to have been quite happy. After he died in 1988, the Soviets issued a postage stamp in his honour. It is a pity the British did not take up Elliott’s suggestion that Philby be given a posthumous CMG (Order of St Michael and St George) for extraordinary services to Britain in a foreign country. It would have been a nice touch, a real upper-class British tease, to let the Soviets think that, all along, their most successful double agent had been double-crossing them.