The curse of modern celebrity is that you're never entirely off-stage. Bill Bailey, one of the country's most instantly recognisable comedians – what with his shortish stature, balding pate, penetrating gaze and greying, hippyish beard ("A hobbit on speed," he once called himself) – is as aware of this as any celebrity. When he's out and about, strangers soon start snapping pictures of him.
"The worst thing is when people try and take pictures surreptitiously," he tells me, jovially incredulous. "I always say, 'Look, you can ask me for a photograph. You will get a much better one than just the side of my face.' Sometimes they just run off. They can't cope."
Treated thus, it's impossible not to feel some sympathy for Bailey; but hard also not to feel a smidgen of understanding for these faint-of-hearts too. For Bailey occupies unusual terrain in our culture. He's got the sort of affability and avuncularity, as witness his appearances on panel shows such as QI, Have I Got News for You and the now defunct Never Mind the Buzzcocks, that make him seem instantly approachable. Yet the scale of his success – and nature of it – makes him slightly intimidating.
He's not only funny, his freeform-seeming material stamped with wry, quizzical intelligence, he's also highly gifted musically. And these two facets have combined to produce something akin to rock-star status. Almost without any discernible effort, as if simply by being his own creatively liberated man, he has redefined the art of what's possible in stand-up comedy.
He has a relish for surreal juxtapositions, memorably colliding Kant's Critique of Pure Reason with the theme-tune from Match of the Day. You could call him the thinking person’s comic, but he's show-off averse. He has described his ascent to household-name status as "meteoric, if the meteor was being dragged by an arthritic donkey across a ploughed field in northern Poland."
His aim down the years has been to see not how far he could go, but how far the comedy could travel. "All kinds of things have gone into my shows – cajun and rock bands, Bollywood, Kraftwerk tributes, effects and so on," he explains. "As long as it services the comedy, everything is up for grabs."
His new show, Limboland, which comes to the West End at the end of the year, marks a shift in direction. At 51, Bailey is slowing down the showbiz spectacle. "I wanted to allow room to let the stories flow," he says.
Born Mark Bailey (Bill was a nickname given to him by a teacher) and growing up near Bath, the only son of a doctor and nurse, he was the school brain-box, was awarded every prize going, and might have gone on to shine in academic circles had his interest in formal education not waned. He eventually dropped out of studying an English degree in London; the impulse to do something else – be in a band, and then make people laugh – proved irresistible. Still is.
"You get to a point where you have time to reflect: how did we get here? I realised that the 'future' is different to how I imagined it," he says. "When I was a kid I thought it would be a bright, shiny Tomorrow's World. It isn't. That's what I wanted to explore in Limboland – as well as where we go from here. There doesn't seem to be any clear path. When I was a kid. Britain seemed to know its place in the world – now we don't."
That perhaps explains why he's an admirer of Jeremy Corbyn. "I am glad he has been elected leader," he says, getting into an impassioned flow. "Whatever happens, it's good for politics… right now he's exactly what people want and need. He has this authenticity. He sounds as if he has his own opinions."
Bailey is scathing – in a comically modulated way – about what he sees as the vilification that has greeted Corbyn's ascension. "He's a bearded vegetarian in a cardigan who has a predilection for hummus… in which case, I am also in the frame as a 'security threat'. It's a measure of the drift to the right in UK and European politics that these traits mark Corbyn out as some kind of dangerous English revolutionary.
"Not singing the national anthem was a PR gift to his detractors, and one I imagine he won't repeat. But it's not a great song is it? It's a bit of a dirge, a bit samey. And the lyrics are rubbish."
Yet Bailey's constituency is broad and able to take the rough of these antagonisms with the smooth of his laidback artistry. He has delivered some nasty barbs about Tories in the past – reworking Candle in the Wind as a mocking send-off to Margaret Thatcher after her death during his 2013 tour Qualmpeddler, for example. But there was no outcry. Where gobbier comics invite opprobrium, Bailey's benign aura as he doodles his thoughts into thin air somehow torpedoes any temptation to get worked-up and indignant.
He's also endearingly old-fashioned. Take his views on social media: "There's a consensus of righteousness. In a way, I wish none of it had ever happened. Facebook, Twitter – if it had never happened the world would have just carried on serenely. It’s utterly redundant and yet we all have to be involved in it somehow."
In Limboland, he takes a few acerbic pops at David Cameron, describing him as "a laminated weasel of a man". But his dislike is not absolute – and fair-minded in its own way, even in the light of the Ashcroft revelations. "Most people, myself included will say, 'Yeah, well, that's the sort of thing he probably did, but that's poshos for you.' Fundamentally, I think he's a decent bloke who's in charge of this rusting hulk that is veering to the right. I still think his is a divisive credo. There's an anger bubbling under the surface. Audiences are p----- off." Bailey has always been a dissenting voice, a rebel at heart.
What next? One thing's for sure, he's not heading into retirement. "I will definitely carry on. I love it," he enthuses. "When I started out 25 years ago, it was a shambles. Now I know how to put a show on. The challenge is to keep it interesting and explore difficult subjects – like talking about our relationship with the Islamic world, and how we feel about constantly being on our guard about offence. But all that’s for the future."
For now, he'd like to win hearts and minds overseas. "The challenge is taking it to new territories," he says, sounding more brand-conscious than Corbyn-esque. I'd wager the huge appeal of this English eccentric is such that thousands more will flock to Baileyland. He'd better steel himself for a lot more of those lone-wolf photographers.
Bill Bailey's Limboland is touring until July 2016, with a five week residency at London’s Vaudeville Theatre Dec 10-Jan 17. Tickets available through Telegraph Tickets; 0844 871 2118. Full info at BillBailey.co.uk