But he has, he admits, always wanted to play a spy – "any actor worth their salt would jump at the chance", he says, "because it's all about mask shifting". His opportunity finally came thanks to Tomas Alfredson, who cast him in his adaptation of John Le Carré's celebrated MI6 thriller – a film that is already being talked about in the industry in hushed, Oscar-worthy tones.

The iconic Cold War spymaster George Smiley is played by Gary Oldman – trading in his usual fire-eating performance for a cloak of impassivity – and Cumberbatch is Peter Guillam, his sidekick in all but name, who puts his own integrity on the line to help him uncover a Russian mole at the heart of the secret service. As eyecatching as the film's 70s aesthetic – gunmetal London skies, stolen documents in buff folders – are the names populating MI6's HQ: Colin Firth, Toby Jones, Mark Strong, Ciaran Hinds, John Hurt and Tom Hardy. "That's a call sheet I'm going to frame and keep for ever," says Cumberbatch.