With lines such as "Don't make me live for my Friday nights/ drinking eight pints and getting into fights", Twentysomething, the title track of Jamie Cullum's breakthrough second album, celebrated the carefree exuberance of being young.

However, the Essex-born pianist never imagined that almost a decade after its 2003 release he would still be singing the same song. The album sold more than a million copies, cementing his place as the biggest selling UK jazz artist of all time. But having turned 30 last year, he is contemplating changing the song's lyrics to reflect his slightly more advanced age.

"It's quite odd singing something like that now because your concerns and preoccupations definitely change as you get older," he says. Surely the song will sound even stranger in 10 years when he will be 40? "I ... imagine I'll still look about 17 years old," laughs Cullum, who attributes the five-year gap between his last album 2005's Catching Tales and his fourth opus The Pursuit - out tomorrow - to the prospect of potential creative burnout.

"A lot of that time was spent on the road touring in support of the last two albums," he says. "I visited every continent two or three times. So when I got back I needed to let my mind become fertile again and get ready to produce some new urgent music."

He believes his music has matured in the intervening years. "My intentions haven't necessarily changed in an obvious fashion," he says. "I've become more confident and able to follow through with my thoughts and feelings." Having previously worked with hip-hop producers such as Handsome Boy Modeling School's Dan The Automator and The Neptunes' Pharrell Williams, Cullum is known for pushing stylistic boundaries.

The Pursuit's most adventurous track is We Run Things, a collaboration with his elder brother Ben Cullum that is based around a house-inspired groove.

"That track is built around a beat that we made quite some time ago," he says. "Initially we were going to give it to someone else but it was so funky that we decided that it had to be on my record."

Ranging from the Massive Attack-sampling reworking of Stephen Sondheim's Not While I'm Around to Cole Porter's Just One of Those Things, recorded at Tony Bennett's Los Angeles studio with the Count Basie Orchestra, The Pursuit combines traditional approaches with contemporary techniques.

"With this album, I tried to very much embrace the love I have for both new and old music," he says. "I grew up in the 90s listening to pop and rock music of the time ... It wasn't until a little bit later that I started getting into jazz. In my mid-20s, I started to try to find a way to bring the two together. "I feel there's a way to mix a kind of classic sound with a sound that's a bit more 21st century - to really make a sound that could only be made in this day and age."

The album's boldest cover is Cullum's take on Rihanna's Don't Stop the Music. "It's part of the DNA of being a jazz musician to reinvent pop songs of the day," he says.

According to Cullum, he often selects such numbers through a process of osmosis. "They're defined not by the fact that I chose them but that they in a funny way chose me," he says. "It's normally a song that has really got inside me and really meant something to me." Cullum married Sophie Dahl (granddaughter of children's author Roald) at a country mansion in Hampshire last month.

The model-turned-food writer also appears on the album, providing backing vocals on Mixtape. She also recommended Nancy Mitford's novel The Pursuit of Love, from which it takes its title. "It's a pertinent reminder that life is about being a journey and not about reaching a destination," says Cullum, who reveals he has been more open with his emotions than on his past records.

"It's not so much that my previous albums haven't been as personal, it's just that I've learned to express myself more honestly and more clearly," he says. "As you get older, you learn more about who you are, which makes it easier for you to express yourself."

He recently made his first foray into soundtracks, composing Grace is Gone for Clint Eastwood's 2008 movie Gran Torino. "Getting to do that was probably the best professional experience of my life," declares Cullum, who met the Invictus director through Clint's jazz musician son Kyle Eastwood. "He's part of the fabric of what makes cinema what it is. Writing that song and recording it in the front room of his house while he was hanging around waiting for me was just amazing."

Cullum hopes to contribute to more movie scores in the future. "I'd like to do more films with people like Wong Kai-Wai, Jim Jarmusch, Paul Thomas Anderson or Spike Jonze," he says. "But I've been spoiled now because having your first film experience with someone like Clint Eastwood is like having caviar as your first meal as a baby."

* The Pursuit is in stores tomorrow