Bob Harris is on a roll. The veteran broadcaster and darling of the country music world has seen his career revitalised in recent years and his role as national treasure well and truly set in stone.

The former Old Grey Whistle Test presenter, who once hung out with John Lennon, George Harrison, Marc Bolan, Queen, Brian Wilson and Led Zeppelin, has become a doyen of American roots music, fêted as an icon in Nashville, with his own national country show on Radio 2 and a string of live events and festivals to his name.

Now 73, he is doing the opposite of slowing down.

This coming week he is launching a national tour of up-and-coming country bands, which begins at the O2 Academy Oxford on Thursday. That comes on the back of his cinematic debut – playing himself in the critically acclaimed Wild Rose alongside Jessie Buckley as an aspiring young country artist.

Jessie plays Rose-Lynn Harlan, a Glasgow single mother of two just out of prison, who is pursuing her dream to become a country music star in Nashville. Her goal is to meet Bob on his Radio 2 show – the real life springboard for so many stars.

“It’s brilliant!” says Bob, in the honeyed tones which have earned him the nickname ‘Whispering Bob’.

“I feel blessed. The film is one of the most thrilling things I have ever done and I was so excited to be a part of it. Jessie is such a major talent so I loved working with her. And seeing it at the cinema was amazing. The reception has been incredible with five-star reviews everywhere.”

Bob’s appearance in the film came about as a result of writer Nicole Taylor’s own fandom.

Bob, who is relaxing at his studio near Steventon, south Oxfordshire, explains: “Nicole was a big fan of Mary Chapin Carpenter, discovered my show and began to love it. This was in the days when there was no country music anywhere else on either radio or television, and I was in the lane alone. So when Nicole began work on the film script, I became central to the story.

“I’m not on screen for very long at all, but am woven into the film through her determination to meet me.”

To celebrate the launch of the film, Bob is hosting a screening at the Ultimate Picture Palace in East Oxford on May 15, where he will also talk about his role in the move and invite questions from the audience.

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Bob at the piano. Picture by Marc West

“I’ll introduce it and talk about my experience as part of the film,” he adds in a voice as warm and richly satisfying as clotted cream on sticky toffee pudding.

We get to hear him before then, though, when he takes to the stage at the O2 Academy Oxford on Thursday for the first night of his Under the Apple Tree UK tour. The shows are headlined by West Country three-piece Wildwood Kin (featuring sisters Beth and Emillie Key and their cousin Meghann Loney) along with bluesy duo Ferris & Sylvester (Issy Ferris and Archie Sylvester) and a local support act, which in Oxford is scorching Americana act Loud Mountains.

“They are people who perform from the heart and really mean what they say,” he smiles.

The tour is an extension of the work of Bob’s Under The Apple Tree sessions, recorded in an orchard behind his home from where he and his wife Trudie run their own independent radio and TV production company, WBBC.

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The sessions are overseen by his talented son Miles with help from the journalist, photographer and Oxford Times contributor Marc West. Bands to have been given a boost by Bob’s patronage include The Shires, Ward Thomas, The Wandering Hearts and tour headliners Wildwood Kin.

“We are an open door for grassroots talent,” he says. “We have three or four sessions a week and continue to support young artists coming through. We don’t bother about the number of Instagram followers they have, it’s all down to the music.

Bob was approached to present the tour by international concert promoters Live Nation. Bob, whose own country show has just celebrated its 20th anniversary, says with satisfaction that the tour reflects the growing popularity of country music in the UK.

“It’s fantastically gaining ground in Britain,” he says. “The Country to Country festival is a sell out and there are new TV and radio stations which, even six years ago, would have been unthinkable.

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“And it all rests on the strengths of the songs; the lyrics ring true and there’s an open-hearted honesty.”

For Bob, who was famously invited by David Bowie to sing on his classic tune Memory of a Free Festival, it’s all in a day’s work.

This, after all, is the man who watched Arthur Brown set fire to his own hair while performing Fire, was spiked with LSD while watching a Bob Marley show with Alexis Korner, who tracked down the elusive Brian Wilson in California and who lived the rock & roll dream touring America with Queen.

“I’ve had a great life,” he reflects. “I consider myself very lucky. We are blessed by being right in the middle of an unbelievable world of musicians. And I’m as enthusiastic as ever.

“I’m blessed. I’m in my 70s and to still be in the heart of things and still relevant is amazing. But it’s all because of how much I love new music – that’s been the engine of everything I’ve done since first stepping in front of the microphone.”

* Under the Apple Tree , O2 Academy Oxford, Thursday, April 25. ticketmaster.co,uk

* Wild Rose with Q&A with Bob Harris at the Ultimate Picture Palace, Oxford, on Wednesday, May 15. 6.15pm