When he begins to play, however, embarking on an improvisation that gradually reveals itself as 'My Funny Valentine', any sense that he is a victim disappears. He plays so beautifully, so strongly - left hand rolling out the bass-line with the force of a piston - that the disparity between frail frame and muscular music ceases to matter. He's probably the best jazz pianist in the world at present and though he seems to have been playing at the highest level for years, he is still only 30. When he finishes the opening number, the applause has lost any sense of a sympathy vote; it's more like a tribute to genius.
To the anticipated question on his size, Petrucciani replies: 'It doesn't make any difference. I would like to make you happy and say that it does, but music is in the mind and in the fingers, it's not really the size of somebody. I am really very lucky. Sometimes I worry myself because I'm so strong; I can stay up for four nights without sleeping, I can do four things at the same time. I'm the kind of person who will die of a heart attack while saying 'Hi] How you doing]'. I push it to the limit; at times it's dangerous but it's nothing to do with my health, it's just my strong willpower.'
Born into a musical family in Orange in the South of France, Petrucciani began playing classical piano as a child but soon abandoned it to concentrate on jazz, performing swing-era tunes with his guitarist father and brothers at local gigs. Taken to Paris by drummer Aldo Romano when he was 16, Petrucciani made a record and immediately established a reputation. At 18 he moved to California where he stayed for four-and-a-half years. The saxophonist Charles Lloyd, who had retired, was so affected by Petrucciani's playing that he built a new band around him.
Petrucciani now divides his time between New York - he speaks English with a feisty NY accent - and Rome, where he lives with his wife, the classical pianist Gilda Butta. The QEH date was one of a series of solo piano concerts to promote his new album, Promenade with Duke, a homage to Duke Ellington, whose records first inspired him to learn piano. It's a remarkable performance, improving on some of the most well- known themes in jazz without any sense of dull duty or self-indulgence. Petrucci ani re-invents each tune in his own image, taking the Ducal elements and transforming them into lively improvisations that sneak his own European references - Debussy's 'Images' say - into the Afro-American jazz tradition.
'I've been preparing this album for 25 years', he says. 'Duke Ellington was the one who made me learn the piano, and I chose the most familiar standards, the most famous songs that he or his collaborators wrote, like 'Take The A Train', 'Caravan', 'C Jam Blues' and 'In a Sentimental Mood'. I'm not so interested in the technical aesthetic of the music, the perfectionism of the playing, as I am in the aesthetic of the sound and the vibration and the silence between the notes. I'm really learning the piano now, really learning how to play. It's very difficult to play Duke Ellington's music and not come out sounding like Duke Ellington.
'When you improvise it's not like playing a classical piece where you rehearse it for many months and then play it almost the same every night. Every concert or record that I do will be totally different. And sometimes you might put your finger in the wrong place, and if everything went well until then you have to be smart enough, or, how you say, brattish enough, to make it look like you did that on purpose. And then you keep going and you go deeper into the error, into the mistake, to make it something right, so minus plus minus equals plus.'
A highlight of the new album is 'C Jam Blues', a one-note invention that he strings out into a virtuoso performance, left hand rolling out the walking-blues rhythm while the right hand takes the melodic line for a Paul Klee-like perambulation, going on and on until the listener wants to laugh out loud with delight, a rare feeling in jazz at present.
The stereotype of the jazz pianist, from Bud Powell to Keith Barrett, is that of the troubled genius. It doesn't fit here. 'I'm at peace with myself when I play,' Petrucciani says. 'I don't believe in suffering artists. I believe you have to be happy, to be in good health, to be rested. The Mozart era doesn't exist anymore . . . dying of tuberculosis in a dirt-hole with people not knowing you exist . . . I'm very, very, happy.'
On stage he performs 'C Jam Blues' and it's quite different from the album. At the interval, to tumultuous applause, he picks up his crutches and walks to his son, who is playing with a toy car in the wings. You almost expect him to fly.
'Promenade with Duke' is out now on Blue Note CDP 7805902 (CD only).