War movies always play fast and loose with the truth. So do science movies. The Imitation Game is a movie about science in war, so it was perhaps inevitable that it would be something of a travesty of both. Ostensibly, it’s the story of Alan Turing, the mathematical genius whose work on the ‘solvability’ of maths problems led him to propose the basic design of a machine that could work out whether a problem was solvable or not before it started working on it.

That’s the basis of modern computing – and also of modern cryptography and decryption. Turing was recruited as a consultant by British Naval intelligence in the late 1930s, and when the Second World War began, transferred to Bletchley Park, the decryption centre established to tackle the ‘unbreakable’ code of the Nazi ‘Enigma’ machine – a task that he and other codebreakers achieved over a three-year period.

In the process they designed the ‘Colossus’, the first machine that had ‘stored programmes’ – that is, wasn’t hard-wired. A monster apparatus of 16,000 valves, it had, essentially, the power of a single microchip. The Colossus design was at the root of the mainframes the US and UK developed after the war.

Turing didn’t live to see the development of a computerised world. In the early 1950s, he was arrested for homosexual activities, and had to choose between jail and what was then known as ‘chemical castration’, a barking-mad process by which he was injected with oestrogen to still his ‘unnatural’ desires. Two years later, he was dead – suicide, as legend has it, by eating an apple he had laced with cyanide powder he had made with household products.

The Imitation Game is happy to take the suicide, the most lurid part of the whole story, since the film’s ‘sense of mission’ is to vindicate Turing as a war hero, persecuted for his sexuality. For that the film has gained some praise, with many willing to overlook the inaccuracies.

But it is most strange, for in trying to restore Turing’s full humanity, including his sexuality, the filmmakers have put his sexuality at the centre of his being, in the most clichéd way possible. Seeking to contest the homophobia of the mid twentieth century, they have adopted and deployed every one of its clichés. It’s a travesty – and that matters – but it’s also instructive about the way that ideology is constructed, how it conforms a resistant past to present needs.

Alan Turing was a middle-class public (that is, private) schoolboy and Cambridge man whose genius at maths was rapidly recognised. By the age of twenty-four, he had written the ground-breaking paper ‘On Computable Numbers’, an extended thought-experiment which applied Gödel’s Uncertainty Theorem (that is, that maths can produce unsolvable problems, in the same way that language can produce undecidable propositions such as ‘this sentence is false’).

From that, he laid down the principles on which a machine capable of problem solving must work. It was the basis for the differentiation of what we know of as the computer from any sort of simple adding machine.

Turing was, like many maths genius, unorthodox, absent-minded, capable of drifting away in thought. By his twenties, he had also decided that he was mostly homosexual. All that adds up to outsider status. Yet Turing was also part of middle-class life: a college man, a competitive team athlete, close with family and friends. He was also politically aware enough to realise, by 1937, that there was going to be a war, and to offer his expert services to the intelligence service, who took him up immediately.

By the time the war started, he had been working with senior naval officers for a couple of years. Once he joined Bletchley Park and became a director of its decryption operations he was running a staff of dozens, and then hundreds, of decrypters, analysts and clerks. Teamwork was essential to decrypting ‘Enigma’, a code system that used a machine to create an ever shifting code within a single message, generating trillions of possible combinations. Turing’s leadership and brilliance consisted in large part in how to assign and then reassemble separate parts of the decoding into a new whole.

Through 1940 to 1943, he consulted with Churchill and other top ministers, and crossed the Atlantic half a dozen times to consult with John von Neumann, the Manhattan project scientist developing the theory of cybernetics. His superiors understood the value of his work, and gave it all the resources and leeway acquired.

None of this has survived into The Imitation Game. Benedict Cumberbatch’s Turing is arrogant, aloof and quick with a putdown. He delights in making his colleagues feel stupid, and in making his superiors guess his actions. He’s bitchy and cute. He sees the war as a bore, a problem to be solved, not a moral-political-national struggle.

None of this accords with anyone’s memory of Turing, but it matches a set of cliches, that of the mid-century capital-H homosexual. ‘Turing’ is, put simply, queenish. The film has simply decided that a certain cultural style of being homosexual can be used to construct Turing’s whole character. There is a strong suggestion that he is a champion decrypter because straight society is a code that the homosexual must crack – and pass as straight within it.

In that way, the film loses all the particularity of the Second World War – the degree to which the national emergency created solidarity, mutual trust and regard. Instead, Bletchley park is rendered as bitchy, backbiting and as individualist as Vogue magazine in The Devil Wears Prada.

But it gets worse. Much worse. In their effort to make Turing into a trickster character, the filmakers have added a lurid and wholly fictional plot in which Turing uncovers a Soviet spy at Bletchley and keeps his secret because he knows of the man’s homosexuality. Later, he conspires with the MI6 agent attached to Bletchley to conceal some results from the higher authorities so that the decrypts wouldn’t be overused.

This was standard practice in any case. The MI6 agent in question turns out to be John Cairncross, head of the Cambridge spy ring, whom Turing never met.

The implication of this are obvious and fantastic. Turing is a natural spy, because, of course, he is a homosexual. It’s deeply ironic, because it is this pre-Stonewall idea of the homosexual – as a natural trickster – that motivated the very persecution of people like Turing in the 1950s as ‘untrustworthy elements’. Indeed, the film implies that Turing has no loyalty to his country or society at all, inventing yet another ludicrous plot in which Turing names the computer he builds ‘Chris’. Who is Chris? Ah, flashbacks reveal it. He is Turing’s only friend at boarding school, a crush, possibly a lover, who died aged 16, from TB. In a frankly Pythonesque scene, young Turing is shown being told the news offhandedly, and retreating into himself, seething with hatred at this cold establishment.

The reality? Turing didn’t have a great time at boarding school, he did lose a friend aged 16, but his schoolmasters recognised their connection, and were solicitous of him. Two days after Chris’s death, Turing wrote a condolence letter to his friend’s mother – because, quite simply, he was an Edwardian, sticking to the external social rules and obligations that formed him. The Imitation Game’s construction of this is self-parodic – essentially, that Turing built a new best friend and it helped him win the Second World War for us.

In reality, the Colossus computer came along when the Engima code had been largely decrypted. Though it was built to Turing’s design, its true architect was Tommy Flowers, the head radio engineer at the GPO research unit, the person charged with building the thing. A working-class boy apprenticed to the GPO at 13, Flowers had the key insight, that ‘Colossus’ should have stored programmes – that is, that the various things a computer did shouldn’t have to be reloaded afresh each time. That is the computer: the thing I’m writing this on, the thing you’re reading it on.

Flowers and his team worked hundred hour weeks for eleven months to build Colossus. He and they appear nowhere in the film.

Instead, we get Turing alone in a shed at Bletchley, putting Colossus together by hand. When the code is cracked, it’s all at once – and they suddenly know the position of every U-boat in the Atlantic. The analogy is obvious, especially if you’ve seen The Social Network: it’s Alan Turing as a proto-Zuckerberg or Steve Jobs, and Bletchley Park as the first start-up, the ancestor of Apple and Facebook. The effect is to attribute all heroic power to the genius with the one big idea, rather than the masses.

‘The war was won by six people in a shed,’ one of Turing’s assistants (actually his colleague) says in the film. But hundreds of people did the work that cracked Nazism’s codes – and millions actually fought the war.

This version of Turing is a geek and a cliched homosexual. But, in in a more conscious transformation, Turing is also politically intersectional, a ‘natural’ champion of women. Thus we see Turing being the only man to take Joan Clarke seriously, the one woman who passed the test set to find highly-talented decrypters.

Later, he offers to contract a sham marriage with her so that her parents will not call her back home. Nothing indicates more effectively that the filmmakers don’t have a clue what about the period they’re dealing with, than that they think parents could call home a woman from essential and top secret war work on a whim, as if 1940 were 1840. They’re also projecting an attitude onto Turing that the didn’t have: his view of gender relations was conventional. Joan Clarke was limited by sexist attitudes and never rose beyond the mid-level ranks to being a full decrypter, which she should have. But Turing never did anything about that. He was engaged to her, for several months, out of mutual love and affection. He broke it off only partly out of a decision that he was more homosexual than heterosexual: it was also because, as he explained to friends, if he married he wanted a traditional wife and homemaker, and Clarke was far too intelligent for that (Clarke is played by the conventionally ravishing Keira Knightly; she was conventionally plain in real life. She went onto a distinguished career in GCHQ, British intelligence, whose details remain secret).

Which gets us to the weirdest thing about the portrayal of Turing in the film. It can’t cope with the full complexity of his sexuality, which shifted over his life, and which we would now call ‘queer’. Mostly sexually inactive through shyness in the 30s, he made clear his ‘tendencies’ to Clarke when they became engaged; she said it didn’t matter much to her. He expressed a desire for family and children. Through the prism of post-Stonewall essentialist ideas of sexuality you could call that sexual false consciousness. But you could also suggest that the film’s transformation of a real engagement into a sham one is an attempt to impose a highly specific idea of sexuality onto the past, one in which one has to be true to a deep and singular sexuality.

This is another self-flattering portrait of Silicon Valley culture, as an inevitable ally of the marginalised – and of the marginalised as the real geniuses, annihilated by the culture they serve. It is Alan Turing through the prism of Chelsea Manning, with ‘Born This Way’ as the soundtrack.

The final scene brings all these absurdities together. It takes place in Manchester at Turing’s house after he has been sentenced to chemical treatment. Joan Clarke visits him. She talks about how she is now married. A latest version of ‘Chris’ the computer burbles away in the living room. She and Turing try to do a crossword together as they used to, but it’s useless. The drugs have killed his mental acuity.

But … but …  but … one wants to shout.

Firstly, the absurd chemical regime lasted a year, after which Turing was free of it – and, increasingly sexually self-confident, became keen on ‘men’s holidays’ in liberal Norway.

Secondly, Turing had long since moved on from computers, to tackle the mathematics of molecular biology.

Thirdly, the injections did nothing to his mental powers. They were nothing more than oestrogen, thus making the suggestion a bit of unconscious sexism on the filmmakers’ part.

Purportedly seeking to liberate him, they have turned this brilliant, multiply-talented and complex man into the clichéd Sad Homosexual, sitting at home alone with the lost love he made out of vacuum tubes. From some quarters the film has gained support for championing Turing. But it’s a tiresome and self-satisfied view of one of the most amazing events in the twentieth century, libelling and diminishing the man it sought to celebrate, and many others as well.