Cookin' with jazz: How Jamie Cullum found perfect harmony

It is 6.30pm and Jamie Cullum is eating his first meal of the day, a chicken croque monsieur. Even so, he urges me to take a couple of mouthfuls. So this is the musician's diet that keeps him so svelte while on tour, away from the culinary ministrations of his new wife, the writer, former supermodel and TV cook Sophie Dahl. We are sitting in a tiny Parisian café a few doors from his hotel and just around the corner from L'Olympia, where Jamie will be performing in a couple of hours.

No jazz artist has enjoyed the same degree of crossover success that Jamie, 31, has in the seven years since his career took off; seven years in which he has sold 4.5 million albums worldwide. Yet there was a time, before he stumbled into the life of a professional musician, when he was living in Paris, sitting in cafés all day, a wannabe Ernest Hemingway trying to write a novel. 'Prior to that I was someone who played music,'he explains. 'I was in bands, played guitar and drums, and the piano. From the age of about 13 I would go to friends'houses and jam – it was always a part of my life. But never did I lie in my bed and think, "God, I want to be a rock star."'

Jamie is here for a two-night fixture performing songs from his latest album The Pursuit, as well as a smattering of tunes from earlier albums and a couple of jazz standards – part of an intermittent tour of European cities. I'd watched him perform a fortnight earlier at the London Palladium, and had been struck by the mixed profile of his audience, from children to seniors. Many fans discovered him through the theme song for the Clint Eastwood film Gran Torino (co-written by Jamie, Clint and Clint's son Kyle), which has turned over more than £200 million gross – the song, that is. New fans are still discovering him through his eclectic weekly jazz show on BBC Radio 2.

On stage, Jamie is an energetic, almost athletic performer, dash-ing about, unwilling to sit still for long. 'I never use a piano stool,'he tells me. 'I always use a drum stool. Because I feel that when you're down there you're playing in that way you're supposed to. I like to be above it.'With ballads he sings sideways across the mic, gazing at the audience, which I suggest he might have got from Elton John. 'When I do that I always feel like Elton. I didn't know much about him until I heard Ben Folds sing 'Tiny Dancer'. I came home and I was trying to learn it, and my mum said it was an Elton John song. I didn't believe her. That's when she dug out Tumbleweed Connection and those early Elton John records. It opened up a whole new world.'

Jamie's mother is Anglo-Burmese, although there is some French blood on her side of the family a couple of generations back, and the moment you know this you can see it in his dark brown eyes and smooth, exotic complexion. His 'very dark-skinned'Indian-Burmese grandfather, who served in the British army, lived in a house with servants in Rangoon until Japan invaded Burma in 1942, when he brought his family to live in Wales. 'I can do a Burmese curry and my auntie makes incredible lime pickle,'Jamie tells me, though he adds that his wife 'doesn't need any cooking tips from me'.

What makes his provenance even more intriguing is that Jamie's paternal grandmother was a Jewish refugee from Prussia, who sang in Berlin nightclubs before the Second World War. His parents lived in Essex and later in Wiltshire, where Jamie attended a private day school. His father worked 'in finance', while his mother has been a school secretary 'for a thousand years'. Both of them, Jamie insists, have the souls of artists but neither had the opportunity to follow an artistic path until late in their lives. 'My mum sings in a choir and my dad plays a bit of guitar,'he says. 'They're both musical and my dad paints.'Because of the difficulties they had in establishing themselves, they encouraged their sons towards stable occupations. 'My older brother Ben broke through that barrier and once he did that they were nothing but supportive. Ben is a musician, a record producer and a songwriter. He's written a lot of songs for my album with me. He writes for other artists throughout the world. Our parents could see that we were driven and they encouraged us. They're incredible people.'

In his London Palladium show Jamie did a song in which he accompanied himself by standing up and strumming the exposed strings of his grand piano and using the wood above the keyboard as a makeshift percussion instrument. 'I used to drum on the table at school,'he says. 'I think a handful of my school reports say that they thought I might have some kind of ADD because I was making sounds. I was far from being an ADD child. I was actually quite quiet and well-behaved. But I used to drum on things. My brother and I would make drum kits out of bins, saucepan lids, cardboard boxes and stuff. And we'd record them. I think when I got to the piano, because I hadn't had years of being told how to do it properly, when I started messing around with it, it just seemed like a natural thing to do. I saw the strings and thought, "Well, why doesn't someone play them?"'He learned to play the piano by ear and to this day can't read a note of music.

By the time Jamie was in his final year studying film at Reading University he had recorded his first album ('which people were buying – admittedly out of the back of my car') and so he decided to move to London and try to be a musician for a year. Sharing a basement flat in Paddington, he was signed to one record company as a solo performer while playing in a rock band that had a record development deal. 'I had piano gigs, was earning my living, paying my rent, living at night-time, writing songs it was a really good time. I didn't expect this stuff to take over.'

This stuff took over principally because of an appearance on Michael Parkinson's chat show in 2003, after which Jamie was offered a £1 million, three-album recording deal with Universal. By the end of that year, his status as Britain's most successful jazz performer ever was sealed. His biggest thrill, however, was getting to play the clubs he'd been going to for years, where his heroes had played – the 606, Ronnie Scott's, the Pizza Express Jazz Club Soho, the Vortex – and realising that he couldn't get tables for his friends.

Jamie met Sophie when they performed together at a fundraiser for the breast cancer charity The Lavender Trust in 2007. He accompanied her on the piano as she sang Nina Simone's 'I Think It's Going To Rain Today'. After dating him for a couple of years, the delicious Miss Dahl became Mrs Jamie Cullum in a register office ceremony a few weeks prior to a vicar's blessing and wedding celebration at Lime Wood, the Hampshire hotel, in January. Sophie arranged for an elaborate circus-style tent decorated with mirrors and stained glass to be flown in from Europe and Jamie performed a medley of songs he had written for her.