The Man Who Knew Too Much, by David Leavitt

Sex, bugs and misread codes

In 2000, the BBC's popularity poll put Alan Turing as the 21st great Briton. Many will have seen him played by Derek Jacobi in Hugh Whitemore's 1986 play Breaking the Code. This dramatic portrayal of Turing's short life, 1912 to 1954, has helped to make him one of the best-known figures in British science. He led the deciphering of U-boat Enigma messages at Bletchley Park, while turning his theoretical computer of 1936 into the practical machine that dominates the modern world. He was also an increasingly open gay man who ended his life with a poisoned apple, two years after his arrest and trial in 1952. But for those who may so far have missed this story, there is a new portal in this book.

David Leavitt, the American gay novelist, has no mathematical background, though he makes considerable efforts to cover Turing's work with a condensation of other books. He has not found new sources, nor used the recently released codebreaking documents; his summary of Turing's Enigma work is particularly thin. His focus lies in applying his interpretation of sexual politics to Turing's texts.

Thirty years ago, homosexuality came to be treated as a political issue analogous to race. Leavitt writes not just as a beneficiary of this liberating transformation, but as one fascinated with finding precursors. So, in discussing Turing's writing on artificial intelligence, his main point is that Turing asserted the equality of machines and minds as a sort of code for the demand for homosexual equality. Turing enjoyed risqué remarks, and his cheeky style had a Wildean detachment from convention. But his wit and colour are secondary to his scientific thesis about the computer and the brain, which comes from putting his theory of computability into the traditional problem of mind and matter: this is the argument that makes Turing's work vital today.

Leavitt loses sight of this central material, and over-eggs his pudding with far-fetched comparisons. Special-purpose machines evoke unrequited love. Bugs in programs suggest the consequences of an unwanted pass.

Turing was a rower who also reached near-Olympic level in marathon running, but his physical presence does not leap from these pages. Leavitt is happier highlighting wispy subtexts than in showing Turing as an active - though often frustrated - player in events. In an online interview, Leavitt even claims of the Enigma work that Turing was merely conscripted: "He had to do it so he did it."

His book belies this: it correctly includes Turing's self-motivated pre-war work on ciphers. But it fails to bring out that Turing took on the vital naval Enigma problem off his own bat, when prevailing wisdom considered it unsolvable. Leavitt depicts Turing's work as theoretical, but as he became the Bletchley Park "Prof", he had to work in very complex circumstances.

For instance, Turing spent winter 1942-43 in America, enmeshed in technical and political negotiation, and writing typically trenchant reports. Leavitt gives little impression of such grasp and responsibility, and barely mentions Turing's role in the technical UK-US alliance, from which so much post-war policy flowed.

Although Leavitt speaks the language of gay emancipation, his storytelling conveys a rather dismal message to the oppressed, of ghetto gloom and doom. He announces Turing's fate even before his birth, so there is no surprise when disaster ensues. Turing's crisis fell in that 1952-54 period which, in The Swimming Pool Library, Alan Hollingshurst used to evoke the source of modern self-affirming gay identity. It was a time when persecution engendered new awareness.

Turing himself responded in this way after the trial in 1952. He got wind of the Scandinavian gay movement, and made a bee-line for Norway. But Leavitt declares that the trial and consequent chemical castration sent Turing into "decline, grief and madness". He ignores the prolific new work of his last two years, except (quite wrongly) to write off his exploratory ideas in physics as deranged.

Deriding English class structure, intolerance and insularity, Leavitt seems unaware that after 1942 the US called the shots and that its "security" criteria came to prevail. How, in that most paranoid Cold War period, did the American authorities react when the top Brit they had trusted turned out to be a shameless homosexual? This needs research quite different from anything attempted by this author.

Leavitt seems oddly unsure of his own verdict on Turing's death, and leaves a feeble conclusion. But Alan Turing's story will still fascinate those who come to it through this book.

Andrew Hodges is author of 'Alan Turing: the Enigma', on which 'Breaking the Code' was based