There are secrets and there are secrets; but one of the best kept secrets in the history of mankind must be that of the wartime activity that happened within that innocent looking compound at Bletchley Park – the home of the code-breakers, whose success is believed to have shortened the length of World War Two by two years, saving an inestimable number of lives. Personally, I feel a certain affinity with the place. As the infant Chrisparkle, I spent my first five years living in the nearby village of Newton Longville; the Dowager Mrs C had a cousin who worked as a typist at Bletchley Park during the war – but of course we never really knew what she did; the Soviet spy John Cairncross, who also worked there, was the brother of the Master of St Peter’s College Oxford, my alma mater. Forsooth, Enigma is the life blood coursing through my veins.

Although Bletchley Park is now open as a museum (and a jolly good place to visit too), many secrets from its past still remain; and that’s probably right and proper, both to protect the innocent and in the interests of national security. But it’s also important that we can consider it a national shrine to the memory of Alan Turing, code breaker extraordinaire, computer creator, and victim of anti-homosexual legislation which required him to be chemically castrated and led him on to suicide. From today’s perspective it seems at best bizarre, at worst immoral and criminal, that he should have been treated this way by the country that owed so much to him; but, as Chapman wrote in 1654, the law is an ass and will always remain so.

The screenplay for The Imitation Game is written by Graham Moore and is based on the biography Alan Turing: The Enigma by Wadham College Mathematics Fellow Andrew Hodges, so it’s got a reliable pedigree. The title comes from Turing’s own words, his description of an experiment to define a standard for a machine to be called “intelligent” – which later became known as the “Turing Test” and which, even today, is an essential concept in the philosophy of artificial intelligence (according to Wikipedia anyway, so it must be true). Interweaving three timelines of Turing’s life – his schooldays at Sherborne, his working life at Bletchley Park and his final days at Manchester – the film tells his story clearly, compassionately and with a good deal of humour. In real life, Turing was doubtless something of a rum cove, too cerebral to waste time on friendships or personal relationships, and too literal to converse normally with his colleagues. This is amusingly portrayed in the scene where Turing is told by one of the chaps “we’re going for lunch” – with the unspoken implication “do you want to come too?” – but Turing only hears and deals with the fact that the others are going for lunch which is a mere statement that doesn’t affect him.

Nevertheless, Turing does have a close friendship with Newnham College alumnus Joan Clarke, a whizz at cryptanalysis, and to whom he was briefly engaged before admitting to her his homosexuality. Turing was definitely turned on by her intelligence – cue for another delicious scene where she is hilariously patronised when taking a test to see if she is brainy enough to work at Bletchley Park. One of the most intriguing things about the film is that it makes you want to find out more about some of the other people in Turing’s orbit at the time – like Joan Clarke, John Cairncross, Commander Alastair Denniston, and International Chess Master Hugh Alexander. Turing’s story has a very rich cast of supporting characters about whom one feels one ought to know something, and the film is definitely a good starting point to find out.

Despite the frequent flashes of humour, and the gathering momentum as the team get closer and closer to cracking the code, the main emotional sense from the film is one of sadness. For me, the two most poignant sequences showed the developing friendship between young Alan and his school friend Christopher Morcom, their messages passed to each other in code to help mask the necessary secrecy of the growing love between them – and how it ends; and the pathetic shell of a man that Turing becomes as a result of the enforced medication to reduce his libido, quaking with tears at the degradation he faces, an old man well before his time.

The film is beautifully acted throughout but boasts at its heart a real star turn from Benedict Cumberbatch as Turing. He absolutely gets that sense of edgy, uncomfortable, reserved intelligence, together with a dedication to his task, a justifiably high opinion of himself and a superior hollowness where his emotion should be. It’s only at the end, when he completely breaks down, that you see the years of repression spilling out, and it’s extremely moving. He is matched by a superb performance from Keira Knightley as Joan, irrepressibly and irresistibly upbeat, and determined to be seen as an equal in the misogynistic world of code breaking. Matthew Goode is excellent as Alexander, his nose put out of joint by Turing’s rise to power, congratulating his achievements with still a hint of resentment; and there’s a brilliant performance by Charles Dance as the no-nonsense Commander Denniston, permanently irritated by Turing’s lack of respect for his position, and always looking for a revengeful way to regain supremacy.

I also very much enjoyed Mark Strong’s quietly assertive and wryly humorous performance as MI6 boss Stewart Menzies; and Allen Leech played John Cairncross almost precisely the same as he plays Branson in Downton Abbey, but seeing as how they’re both socialists in a world of nobility, I guess that makes sense. Topping and tailing the timelines of the story I was very impressed by Alex Lawther as the young Alan – repressed, tight-lipped, tentatively pushing at the open doorway of a burgeoning relationship – and Rory Kinnear is as eminently watchable as he always is as the apparently sensitive, but ultimately law-enforcing, Inspector Nock.

An engrossing story of one of the most important aspects of the Second World War, lucidly told, and compellingly acted – we really enjoyed it. It also gives you a lot to think about secrecy, intelligence, loyalty and justice. This one’s going to be around for a long time – and it’s got to be in line for loads of awards!