Croydon, UK: Blink and you might miss Dan Stevens these days. Not because he has disappeared since his departure from Downton Abbey – indeed, the Cambridge- educated actor’s film career is going from strength to strength – but because Stevens recently lost about 2st (13kg) to play a Brooklyn drug dealer in a new film and is looking very slender indeed. ‘In English terms, I think I’ve lost two or three chins,’ he says. ‘I haven’t been on a horrid diet or anything, just living a bit more cleanly, but I don’t think I would have done it had it not been for work. I’ve had to give up booze for a start.’–MN

It has been a year of transition for Stevens, who is every bit as affable as his Downton persona suggests. The shock death of his character, Matthew Crawley, aired on Christmas Day last year, with outraged viewers claiming their festivities had been ruined by the car crash finale.

But by that time, 30-year-old Stevens, his wife and their two children had already upped sticks and moved to New York, where he was appearing on Broadway alongside Oscar-nominee Jessica Chastain in The Heiress.

Next came a role in forthcoming Brooklyn crime thriller A Walk Among The Tombstones alongside Liam Neeson. And Stevens has just finished filming with Benedict Cumberbatch for the much-anticipated WikiLeaks film, The Fifth Estate, which already has Julian Assange hot under the collar.

It’s certainly a far cry from the safe Sunday night exposure of Julian Fellowes’s cosy costume drama.

‘Well, it was always a risk leaving Downton,’ says Stevens. ‘But I’ve tried to harness that sense of adventure. New York is a very exciting city. How long we will stay there, I don’t know but we’re really enjoying it for now.’

Stevens seems like a man who stays true to his roots, though. Historical romance Summer In February, which he produced as well as stars in, is not only the perfect vehicle for his very particular brand of good-natured respectability, it is also a labour of love that has been in production for more than a decade.

Based on a book by Jonathan Smith, Stevens’s teacher at Tonbridge School in Kent, it is the true story of enigmatic beauty Florence Carter-Wood (played by Emily Browning), who abandoned a well-to-do life in London for a bohemian artists’ commune in Lamorna, Cornwall shortly before World War I.

Here, she falls in love with two men, decent Army man Gilbert Evans (Stevens) and magnetic painter AJ Munnings (Dominic Cooper). Tragedy ensues amid the sun-kissed cliff tops of Cornwall.

Stevens, who was born in Croydon, Surrey, adopted at birth by two teachers and later won a scholarship to Tonbridge, owes a lot to Smith, who directed him in several early roles including Macbeth and went on, says Stevens, to become ‘a great friend and mentor’.

‘I have always had a lot of fondness for Jonathan and for his work,’ he says. ‘He nurtured my early interest in acting and believed in me from an early age.’