What a difference a decade makes … the last time I interviewed the phenomenally successful British jazz-pop star Jamie Cullum he was newly engaged to model and writer Sophie Dahl and was promoting his fifth album, The Pursuit.

Now, as a father of two young daughters, he has found a new rhythm to his life – and, as he approaches the big 4-0, he is rushing around less and spending more time standing still and taking stock.

Not that you would know it from his stage performances – which feature little in the way of standing still, and are as energetic as ever.

The subject of age – and the changes in outlook that can come with it – is a recurring theme in our chat. Cullum, who will bring his quartet to BBC Music’s The Biggest Weekend event in Perth on Friday May 25, is currently working on his eighth album and was last widely seen by the public playing for the Queen at her televised 92nd birthday bash at the Royal Albert Hall.

It wasn’t the first time Cullum had performed for the Queen, but it was – he laughs – the first that he can clearly remember. The previous occasions are foggier memories glimpsed through a haze of youthful high living, though he does recall the late Alan Rickman reading poetry and the Queen requesting that he sing In the Wee Small Hours Of The Morning. He says: “These opportunities, as she gets older and as I get older, I appreciate them more – you appreciate consistency in people because it’s very easy to be inconsistent.”

That doesn’t seem to be a description that can be applied to Cullum, who is as chattily eloquent, down-to-earth and friendly as he was right back in the early 2000s – when he was a regular visitor to such lost venues as Henry’s Jazz Cellar in Edinburgh – before a 2003 appearance on the Parkinson show catapulted him into the public consciousness and he went, almost overnight, from playing in that much-loved basement jazz club to performing at the Usher Hall when he came to Scotland.

Not only does the mop-haired superstar rail against inconsistency; he has also begun, recently, to filter out the more superficial and throwaway aspects of modern culture – in a quest for self-improvement. Rattling off a huge list of his favourite poets – “Rilke, Carol Ann Duffy, Charles Bukowski, Seamus Heaney, Ted Hughes” – he explains that his love of poetry has been creeping into his work of late as he puts together his first album of entirely original material, which is scheduled for release later this year.

“I’m thinking that if you overdose on garbage then garbage comes out. I’ve been trying to fill my brain with wisdom, in the hope that even 1% comes out. It’s so easy these days to input surface stuff when you’re rushing about. I think for me it’s about remembering what you really value. When you rush around, you grab for the nearest thing. Now I have kids, you think about what has value, what enriches life – reading, family, friendships, food, wisdom … I hope it comes out in my work.”

With his 40th birthday looming next year, the always self-aware Cullum is particularly contemplative these days. “I’ve started to look back more, wresting out some of the wisdom I might have accrued and maybe missed. That’s bit of a theme just now. I’m trying to take stock.”

While some get their kicks from cocaine – as Jamie Cullum didn’t sing when he performed a typically funky version of the classic Cole Porter number at the Queen’s birthday party last month and used Porter’s alternative, less risqué, line – others, including the singer himself, get their kicks from reading. Literature has played a huge part in Cullum’s life – from his days at Reading University, where he studied English, to his relationship with Dahl which was born from the shared love of books (“and eating and dancing”).

“We definitely connected over that,” he says, “and we do live in a house of books.” The title of the album he was promoting when we last spoke came from the title of Dahl’s favourite book, Nancy Mitford’s The Pursuit of Love.

Of course, the afore-mentioned Cole Porter, a particularly elegant and sophisticated songwriter, has been a consistent favourite source of material since Cullum first started out (there are no fewer than three Porter songs on his 1999 debut album, Heard It All Before) and if you’ve ever attended one of his gigs, you will probably have heard his take on Just One of Those Things or I Get A Kick Out Of You.

“I love Porter’s dry acerbic wit, and his combination of happy and sad, tragic and comic. He expresses the general struggles we all face. …” Breaking into song at his piano, Cullum continues: “This one, What Is This Thing Called Love, is just great. It shows that understanding of the tragic nature of all things. Porter has very much inspired my writing. In fact, up until a few years ago, my influences were musical – but now they are much more literary. I’ve been looking at composers writing from a lyrical place – a lot of the great writers were lyricists: Johnny Mercer, Stephen Sondheim. They come from a lyrical place. I’m hoping their influence will show in my songs.”

Commenting on a quote he gave another interviewer a few years ago about aspiring to play George Gershwin’s Rhapsody in Blue on the piano one day, he says: “I’ve actually just started learning to read music – and getting into theory with a view to expanding my horizons. I want to get better. I didn’t read music at all until recently. Now it’s a bit like reverse engineering – I look at my fingers and I understand what I’m doing and why things work.

“I’m thinking seriously of going to uni to study music – for selfish reasons. Yes, Rhapsody is still very much an ambition - but right now, I’d be happy with getting through Grade 2 for Beginners – that would be a joy! That comes from the children – seeing their sense of accomplishment. I’m drawn to these moments.”

Jamie Cullum plays at BBC Music’s The Biggest Weekend, at Scone Palace in Perth on the afternoon of Friday, May 25. For more details and to buy tickets (£18 + £4.50 booking fee), visit the website www.bbc.co.uk/biggestweekend

The biggest weekend – other highlights of the Friday programme

Main stage, 2-6pm

Scottish National Jazz Orchestra, directed by tenor sax star Tommy Smith and featuring the crème de la crème of Scottish jazz musicians (including pianists Brian Kellock and Pete Johnstone) will be playing music by Leonard Bernstein and Duke Ellington.

BBC Scottish Symphony Orchestra Celebrating Andrew Lloyd Webber. As the world’s favourite composer of hit musicals turns 70, the BBC SSO is joined by singers Mica Paris and Michael Xavier for what will undoubtedly turn into a birthday singalong.

Main stage, 7.30-10pm

Scottish songwriter and musician Karine Polwart sings songs which combine folk influences with themes as diverse as Donald Trump’s corporate megalomania and the complexities of modern parenthood.

Maverick classical violinist Nigel Kennedy will be playing music by Bach and Gershwin with the BBC Scottish Symphony Orchestra.