If Riley relished Mirren's being playful, he sounds less enamoured with the project he has just finished. For the past six months he has been travelling all over America, shooting Walter Salles' adaptation of Jack Kerouac's On the Road. As Sal Paradise, Kerouac's autobiographical narrator, Riley heads a cast that includes Garrett Hedlund and Kristen Stewart.
Riley had to get fit – "my mum calls me a streak of piss" – and spend four weeks in a beatnik bootcamp. He pulls a face. "Don't fucking ask." Did they all get stoned? "We were allowed to, but not encouraged. I'm a 30-year-old who used to smoke for breakfast, but the Americans smoke super-strength skunk so I stuck to my hash. Kerouac experts talked to us, we watched films, learned the difference between Charlie Parker and Dizzy Gillespie."
And how was Stewart, star of the Twilight films, one of the biggest – and, according to the tabloids who won't leave her alone – grumpiest actors in the world? "She's just 20! The tabloids can fuck off! She wasn't grumpy at all. She was a bit of a Rapunzel character in her hotel suite, not wanting to come to the bar to spend all evening having her photo taken."
When Riley was in America, he missed his wife and new friends in Berlin badly. How is his German? "Super! Fantastisch! When I initially started going out with the lads, with Alex's old school friends, they all spoke English. After a while, though, they expected me to learn German. Alex was born in Romania and she speaks Romanian with her parents, so I understand a bit of that too."
The Leeds lad who was folding T-shirts not so long ago has done pretty well for himself. "Yeah, I got myself a career, met my wife, moved to a new city, learned some languages. I still pinch myself." He is still, however, sleeping 14-hour days to recover from playing Sal Paradise. "On the Road was a hell of an experience so I'm planning to take a break." He grins and looks very pleased with himself. "For now I'm going to be a hausfrau."