"You Just Defeated Nazism with a Crossword Puzzle"

I work in science communication so I probably know more than many about the brilliant mathematician and computer science pioneer Alan Turing. Yesterday, I had a long meeting in the Turing Room, and my journal celebrated the 100-year anniversary of his birth in 2012, sixty years after his conviction for gross indecency and a year before he was eventually given a posthumous royal pardon. But you don't have to know a great deal about Turing to enjoy Morten Tyldum's new film The Imitation Game, which explores Turing's role in the cracking of the Enigma code. I went to see the movie on Friday night with a diverse group of people and we all really enjoyed it.

Turing is played by Benedict Cumberbatch, who puts in a really top notch performance. The movie flits seamlessly between three time periods: World War II, as Turing is hired — barely — to join a team of mathematicians and engineers at Bletchley Park to crack the supposedly unbreakable German Enigma code machine; Turing's schooldays in the late 1920s; and the darker years of the early 1950s when Turing is investigated by the police, suspected of spying for the Soviets, and then of the aforementioned gross indecency.

When he arrives at Bletchey, Turing is hardly the most popular of employees. In fact, he is only hired by Commander Denniston (played by a sneering, Tywin Lannister-esque Charles Dance) because Winston Churchill commanded it. Turing takes over from Hugh Alexander (Matthew Goode), whose team has been making slow progress, and fires the dead wood. He then recruits several crossword enthusiasts including — shock, horror! — a woman, namely the mathematician Joan Clarke (Keira Knightley), with whom he develops a friendship.

It isn't long before Turing makes a breakthrough: "What if only a machine can break a machine?" he asks. With a huge government grant of £100,000, he sets about building such a machine that he calls Christopher and which would eventually become known as a Turing machine. But Denniston and MI6 man Stewart Menzies (Mark Strong) aren't convinced that they will see a return on their investment and Turing and his team are given an imminent deadline for their work. Will they be able to crack Enigma in time?

Most people probably know the outcome and also know that Turing took his own life in 1954 after being convicted of gross indecency and offered the horrific choice between prison and chemical castration (he took the latter). The Imitation Game ends shortly before then, and it is an emotional but understated ending.

Despite the shocking recency of the UK's former barbaric anti-gay laws and despite the tragedy of Turing's death, the film works very well as a celebration of his often isolated and all-too-short life. It's also quite funny in places, mainly when Turing is standing up to Denniston and Menzies, and when he is trying to do things he sees other people do but does not understand, including jokes and flirting. It reminded me a little of The Social Network — Cumberbatch's Turing is not dissimilar to Jesse Eisenberg's portrayal of Mark Zuckerberg, and although both films are, at their heart, about the cracking and the writing of code, their respective directors manage to tell a much more complex and interesting story.

Cumberbatch really stands out in a great ensemble cast but Alex Lawther, who plays the young Turing, is also excellent, and Knightley does well in a somewhat two-dimensional role. The Imitation Game is a moving, compelling portrait of a fascinating man and it's definitely worth a watch.