A piece of Reece Ritchie

I'd expected Reece to be a bit of a pampered boy, his exquisitely symmetrical features and pleased-with-himself pout suggesting he took Dolce & Gabbana suits as his due. He's a brand ambassador for the Italian label's menswear, which celebrates its 20th anniversary this year. In fact he's a cheery lad from Lowestoft, a pepperpot-sized charmer who freely admits that being dressed by Dolce & Gabbana is 'amazing' and bursts out laughing when I ask if he considers himself sexy. 'Erm, thanks very much!' He takes his craft seriously, 'but not too seriously – acting isn't brain surgery.'

Aged 23, he has already made three major films: the caveman epic 10,000 BC, in which he starred opposite Camilla Belle; The Lovely Bones, Peter Jackson's adaptation of Alice Sebold's novel; and the forthcoming Prince of Persia, in which he plays Jake Gyllenhaal's athletic sidekick, Bis. He has played roles as ethnically diverse as Indian American (Ray Singh in The Lovely Bones) and a Persian warrior, though in fact his father, who worked on an offshore oil rig, is from Durban, South Africa, and his mother, a dietician, is English. 'She's blonde with blue eyes,' he explains. 'I'm a straight mix.'

His paternal grandparents left South Africa when Reece's father was a year old. 'I think they came over because apartheid was going on and there was a lot of social unrest. My grandmother had a different skin tone to her little sister and they were given different cards and separated on the bus. Imagine that – she was meant to be looking after her little sister but one of them had to sit up at the top of the bus and the other had to go to the bottom. Obviously my grandparents had aspirations for my dad and his sisters. I'm glad they did. I love being a Brit. I love our dryness, our dark sarcasm. You try it in America and it gets lost; there are just blank faces all round.'

Reece is the middle of three Rs: his elder brother Ray works with children who have learning difficulties; his sister Ria is an aspiring R&B singer. 'I had a good childhood. Down-to-earth. Holidays at Butlins when money was tight.' Was that fun? 'We made it fun.'

He currently lives alone near Lowestoft, in a 1920s Art Deco flat with big windows overlooking a river. 'It's my secret bat-cave. I go back there to recharge my bat-ness.' And his biceps: he has fitted a pull-up bar he uses every time he goes through the living-room door.

Most of his teenage summers were spent with the National Youth Theatre. 'They let me in when I was 15, a year early. I remember my audition so clearly. I did something from Hamlet and sang 'On The Street Where You Live'. I didn't eat for a day before, just couldn't eat.' At NYT summer camp he fell in love – 'many times; there were beautiful, beautiful girls' – and became firm friends with 'Smithy', Matt Smith, the new Doctor Who. 'He was Thomas Becket in Murder in the Cathedral, I was his knight holding his staff.'

After A levels, Reece went to East 15 Acting School – 'the only one that would let me in'. But he's never doubted his charisma: once, at a stadium rock concert, he was having trouble finding his brother, telling him by mobile phone: 'I'll start a Mexican wave to show you where I am.' Within minutes he had done exactly that.

Halfway through his drama degree he was spotted performing a monologue at the Soho Theatre, cast by Roland Emmerich (director of Independence Day) in 10,000 BC and whisked off to learn how to skin animals and grunt at 'prehistoric camp' in South Africa. He filmed in Namibia, New Zealand and South Africa for six months. 'Five-star accommodation all the way. It still blows my mind,' he says.

He has also done his fair share of television slog, appearing on The Bill and 'going through horrible, peculiar auditions'. Such as? 'For Shameless, I had to go to Manchester and pretend to be a physically and mentally handicapped chap singing 'Champagne Supernova' with a lisp and a club foot. The character was meant to be a con man who pretended to be disabled. But it was written out in the end. If my audition tape ever surfaces I'm suing.'

Most of his career, though, has been pretty fabulous. Filming Prince of Persia in Morocco, he would hang out by the pool at the Es Saadi Palace Hotel with Gemma Arterton, 'Fred' Molina and Richard Coyle, playing under-water Chinese whispers. 'Awesome game.' Meanwhile, on set, Jake Gyllenhaal taught him about 'technicalities like rolling resets, pacing, matching up sequences filmed out of order and how to make things easier for the editor...' He sounds wise but dry. 'Jake? No, he's a joker, a rascal.'

A young man with nice manners, Reece tries to take a stand against inequalities on set, such as the times when, during a cold night's filming, the leads wear heat packs but the extras – 'who might be quite elderly' – have to do without. 'It's just common decency, isn't it?' Reece calls a film set 'a dangerous, sexy, intense place' but keeps his liaisons private. 'It's all well and good as long as no one finds out,' he says.

His family are most important to him at the moment anyway. He took his mother to meet Prince Charles at the premiere of The Lovely Bones. 'We sat by him during the film and we could see when he was crying.' Royal tears, eh? 'Yes, and they were actually blue. Really. Glistening blue.'

Prince of Persia: The Sands of Time is out today