So far, so good. The six-figure album deal that pushed Jamie Cullum out of the jazz buffs' columns and on to the front pages this spring seems to have left his tousled head much the same manageable size.
On the evidence of a return to the Pizza Express Jazz Club, the 23-year-old British singer and pianist appears to have gained confidence without sacificing his easy congeniality, sharpened his keyboard attack, given his trio a licence to turn up the heat - and significantly deepened his grasp of emotional songs, even within the nine months or so since his last appearance at the same venue with the same partners.
Cullum has also learned a lot about the pacing of a set. He began on Saturday by hand-drumming on the piano lid against Sebastiaan de Krom's peppery snare-drum crackles and rolls. Then he sat down to a rocking funk-piano vamp and launched into a vocal on It Ain't Necessarily So in a manner somewhere between Kurt Elling and Stevie Wonder.
In the song's later stages, he took to his feet, microphone cradled in both hands, relying only on De Krom's surefooted groove and bassist Geoff Gascoyne's rolling countermelodies for support.
Pointless Nostalgic - the title track of Cullum's current album, co-written with his brother Ben - emerged after a colourful, slowly swinging piano intro full of Keith Jarrett-like chordal clamour. Cullum is no Jarrett, of course, but he takes from contemporary pianists just what he needs. I've Got You Under My Skin was a showcase for his languid young-Sinatra sound.
Having stood once again to eyeball the room, the singer came to a dead halt on the line "Just the thought of you makes me stop -", then wandered idly off to the piano again and picked up with "- before I begin", just when everybody had concluded he was going to start something different. It was an unmistakeable sign of a young star completely sure of his material and his listeners.
Another Ben Cullum piece, These Are the Days - "a summer anthem for the dumped", as Jamie announced it - suggested, with its gospellish spark, that the originals for his next album, due out in September, are likely to meet the standard set by Pointless Nostalgic. Guy Barker then arrived to lend his bright and glossy trumpet variations to a very fast But Not for Me, ignited by Gascoyne's nimble walk and Cullum's casually complex scat.
A superb Blame It on My Youth - a mix of oblique regret and carefully paced revelation, with Cullum's characteristic upturned note-bends and Barker's high-register obbligatos - was a startling example of the leader's evolution since late 2002, when he delivered the same song from this stage. And Radiohead's High and Dry was almost as hypnotic, in both Cullum's subtle singing and the darting treble commentary of his piano-playing.
· At the Barfly, London NW1, on July 1. Box office: 0870 907 0999.