Benedict Cumberbatch is impeccable as Turing, finding the humanity at the heart of The Imitation Game.

Typical. You wait years for stirring tales of British ingenuity and wartime innovation and then two come along at the same time. There’s a great deal of overlap between the story of Robert Watson Watt’s pioneering work to create radar in “Castles In The Sky” and Alan Turing’s quest to crack Nazi Germany’s impenetrable Enigma code in “The Imitation Game”. The stark differences come when the respective films focus on their heroes. Although both mens’ work would be classified and shrouded in secrecy for many years before their true contributions to the modern world could be understood and appreciated, the tragedy of Turing’s case is that the secrecy of his work was just one more deception that he was forced into.

The title “The Imitation Game” (a quote from one of Turing’s own papers) almost sounds like it should be a high-octane contemporary espionage thriller but the film is instead a powerful and fascinating character study of the man himself, examining both his lonely and miserable early life at boarding school and his astonishing wartime work from the vantage point of a police interrogation room in 1950s Manchester. By framing the main narrative with Detective Knock’s dogged pursuit of Professor Turing, believing he is hiding something, the film cleverly underpins everything we see with the awareness of the awful and, from a 21st century point of view, inhumanly cruel fate that would befall the man who Churchill himself once stated had done more than any other individual to help win the war.

The film, the English language feature debut of Director Morton Tyldum, handsomely recreates 1940s wartime Britain and, as you’d expect, there’s a lavish attention to period detail but it never really manages to feel cinematic. Instead it puts you in mind of a prestige television drama, and the effect isn’t helped by the decision to use mostly archive footage of the war interspersed with a couple of lacklustre recreations replete with surprisingly poor CGI flames. The saving grace of “The Imitation Game” is the big name cast who all step up to the mark to do the man, his life and his legacy justice and more than compensate for the lack of visual flair.

Great supporting turns from the likes of Charles Dance as the sceptical Commander Denniston, forced to tolerate Turing’s high handed manner thanks to Churchill’s personal intervention and a playfully steely Mark Strong as Stuart Menzies, a shadowy figure from the newly created department MI6 give texture and interest to the ongoing, potentially dry challenge of using mathematics to break the Enigma code. In the 1952-set scenes, Rory Kinnear, as the determined detective Knock does a fantastic job with his limited screen time, managing to wring out every emotional beat from his character’s growing realisation that his actions will only have helped destroy a great man. But the film belongs to Kiera Knightley and Benedict Cumberbatch. I can’t recall Knightley ever being as good as she is here, and as much as this may be her career best performance it simply can’t compete with Cumberbatch’s portrayal of Turing himself. It’s a magnificent performance, compelling and captivating; utterly distinct from his other iconic role despite the occasional closeness of the personalities. His Turing, high-handed and supremely confident in his abilities, nevertheless beautifully captures a man in all his human frailty, burdened by the weight of too many secrets and still nursing the hurt of the loss of his first love.

Turing was deservedly granted a posthumous Royal Pardon in 2013 but this film serves as both a history lesson and a pointed commentary on diversity and equality. While it pulls its punches somewhat in respect of portraying Turing’s sexuality, there’s no escaping the repugnant truth that, as a nation we rewarded his phenomenal contribution to winning the war by condemning his sexuality, chemically castrating him and driving him to an apparent suicide. This film is another important step in recognising the man for his achievements and acknowledging the terrible way he was treated by the very people he worked so hard to save.