It seems he knows just about everyone from the meanest Chicago bluesmen to members of the Royal Family. Out of all the stars jostling for positions behind the Queen and Prince Charles on stage at the Jubilee concert, none perhaps looked quite as comfortable as Jools Holland.

‘Poshstock’, as Oxfordshire’s Cornbury Festival is known, may not seem quite so posh to Jools in two weeks’ time after all his Diamond Jubilee hob-nobbing on The Mall.

But then the former Squeeze man is already something of a fixture when it comes to summer festivals in Oxfordshire, with few better equipped to get a party going come rain or shine than Jools Holland and his Rhythm & Blues Orchestra.

He can uniquely claim to be a grand-slammer when it comes to Oxfordshire’s big summer outdoor musical extravaganzas, having played to audiences at Cornbury, Henley, Stonor Park and Cropredy, where even the folk fans took to the Holland brand of pure boogie-woogie.

“I’d known about Cropredy for years. But I’d always assumed Cropredy was in the Shetland Islands because of the name,” he chuckles. But winning over all those Fairport-loving folkies was achieved as effortlessly as appearing between Alfie Boe and Grace Jones at the Jubilee concert.

“The music we play — swing and ska — is full of gaiety — like a lot of folk music,” said Jools. Besides, as he is quick to point out: “If you put together my big band, the open air and beautiful Oxfordshire countryside, well, it’s a giddy mix.”

The money that Oxfordshire music impresario Hugh Phillimore has ploughed into the Cornbury Festival down the years has certainly left his accountant feeling giddy since he staged the first festival in 2004 on the estate of Lord and Lady Rotherwick in West Oxfordshire.

Despite attracting acts of the calibre of Joe Cocker, Paul Simon and Robert Plant — with Chipping Norton Set members such as David Cameron, Jeremy Clarkson and Alex James usually to be found in the audience — it has constantly lost money, with Mr Phillimore continuing to insist that “it takes time for a festival to break even”.

After seven Cornbury Festivals, the business went into liquidation owing creditors almost £1.5m.

But even this and a fall-out with Lord Rotherwick were not enough to lay Cornbury to rest.

Mr Phillimore simply upped sticks last year and moved his festival to the garden of another ‘local pile’, Great Tew, a few miles up the road, where it is soon again being staged, with James Morrison headlining on June 29, Elvis Costello on June 30 and Jools Holland on July 1.

For the ‘boogie-woogie man’, the festival’s disappearance would have been a terrible loss to music lovers.

“I’ve played there before. It’s a great festival, with great atmosphere and well organised. It’s big enough to get world-class acts and small enough for people to enjoy them.”

In tough times, for both festival organisers and bands he believes, the key is to draw on wide musical roots.

“The more of a mix in music the better.”

He certainly practises what he preaches, pointing to the fact that his orchestra contains such diverse talents as legendary 77-year-old trombonist, Rico Rodriguez, one of the first and most distinguished living ska artists; the ex-Soft Cell, synth pop pioneer Marc Almond; and soul singer Ruby Turner.

Any suggestion that his friendship with the Prince of Wales and the Duchess of Cornwall, his big society wedding to Christabel McEwen (the former wife of the 7th Earl of Durham) and his appointment as Deputy Lieutenant of Kent, mean that he is as posh as anyone at Poshstock this year — perhaps with the obvious exception of the Dragon School and Eton educated Hugh Laurie — does not go down well.

“If by posh you mean a handsome, superb piano player, well, yes. How posh is Oxfordshire compared with Deptford?” he replies, alluding to the poor household in south London where he grew up.

He could point to the fact that he spent the Queen’s Silver Jubilee playing keyboards outside his local pub in Deptford. Watching the footage recently he declared it looked like “something out of The Sweeney”.

Last Saturday the nation’s favourite piano maestro re-examined his real musical roots for a BBC2 documentary, where he embarked on a personal journey through the streets, historical landmarks, pubs, music halls, and rock ‘n’ roll venues of London to uncover a history of the city through its songs.

His investigation identified many ingredients of a salty tone that could be called “the London sound” as he tracked through the centuries from the ballads of Tyburn Gallows to the Caribbean sounds and styles that first docked at Tilbury with the Windrush in 1948.

Along the way, he met musicians such as Ray Davies, Damon Albarn, Suggs, Roy Hudd, Joe Brown, and Eliza Carthy.

His regular BBC 2 show Later with Jools Holland, which is in its 40th series and once viewed as an alternative to Top of the Pops, has easily outlasted the chart show, with Jools effectively the last man standing when it comes to pop/rock/blues music shows.

“I have an enjoyable balance that I have managed to maintain. I’ve been privileged to have a fantastic job. The band takes up most of my time. We tour all the time. It is the most rewarding thing, playing to give people joy.

“As you get older, you worry less about what people think of you, you play what you enjoy. The great thing about music is that you can communicate how you feel without using words.”

When I suggest The Tube, the seminal programme he presented with the late Paula Yates in the 1980s, marked something of a golden age in youth television, his take is unsentimental.

“It certainly was not a golden age for music. I would call the 1930s and 1940s golden ages.”

But unlike some of his superstar friends he resists rubbishing the likes of The Voice and The X-Factor as glorified karaoke, stifling real musical talent.

“You have to apply a different criteria to shows like that. If it gives some people a break, well, that’s great.”

In its second year at Great Tew, you suspect the Cornbury Festival could do with a break or two, not least with the weather. The performance of the Rhythm & Blues Orchestra and its irrepressible leader will be altogether more reliable.