In the thin drizzle of a Monday night in Sheffield, a crowd of young women are waiting for the Mighty Boosh or, more precisely, one half of it. Big-boned Yorkshire lasses, jacketless and unshivering despite the autumn nip, they look ready to devour the object of their desire, the fey, androgynous Noel Fielding, if he puts a lamé boot outside the stage door. “Ooh, I do love a man in eyeliner,” sighs Natalie from Rotherham. She’ll be throwing sickies at work to see the Boosh show 13 times on their tour, plus attend the Boosh after-show parties and Boosh book signings. “My life is dead dull without them,” she says.

Nearby, mobiles primed, a pair of sixth-formers trade favourite Boosh lines. “What is your name?” asks Jessica. “I go by many names, sir,” Victoria replies portentously. A prison warden called Davena survives long days with high-security villains intoning, “It’s an outrage!” in the gravelly voice of Boosh character Tony Harrison, a being whose head is a testicle.

Apart from Fielding, what they all love most about the Boosh is that half their mates don’t get it. They see a bloke in a gorilla suit, a shaman called Naboo, silly rhymes about soup, stories involving shipwrecked men seducing coconuts “and they’re like, ‘This is bloody rubbish,’” says Jessica. “So you feel special because you do get it. You’re part of a club.”

Except the Mighty Boosh club is now more like a movement. What began as an Edinburgh fringe show starring Fielding and his partner Julian Barratt and later became an obscure BBC3 series has grown into a box-set flogging, mega-merchandising, 80-date touring Boosh inc. There was a Boosh festival last summer, now talk of a Boosh movie and Boosh in America. An impasse seems to have been reached: either the Boosh will expand globally or, like other mass comedy cults before it – Vic and Bob, Newman and Baddiel – slowly begin to deflate.

But for the moment, the fans still wait in the rain for heroes who’ve already left the building. I find the Boosh gang gathered in their hotel bar, high on post-gig adrenalin. Barratt, blokishly handsome with his ring-master moustache, if a tad paunchy these days, blends in with the crew. But Fielding is never truly “off”. All day he has been channelling A Clockwork Orange in thick black eyeliner (now smudged into panda rings) and a bowler hat, which he wears with polka-dot leggings, gold boots and a long, neon-green fur-collared PVC trenchcoat. He has, as those women outside put it, “something about him”: a carefully-wrought rock-god danger mixed with an amiable sweetness. Sexy yet approachable. Which is why, perched on a barstool, is a great slab of security called Danny.

“He stops people getting in our faces,” says Fielding. “He does massive stars like P. Diddy and Madonna and he says that considering how we’re viewed in the media as a cult phenomenon, we get much more attention in the street than, say, Girls Aloud. Danny says we’re on the same level as Russell Brand, who can’t walk from the door to the car without ten people speaking to him.”

This barometer of fame appears to fascinate and thrill Fielding. Although he complains he can’t eat dinner with his girlfriend (Dee Plume from the band Robots in Disguise) unmolested, he parties hard and publicly with paparazzi-magnets like Courtney Love and Amy Winehouse. He claims he’s tried wearing a baseball cap but fans still recognise him. Hearing this, Julian Barratt smiles wryly: “Noel is never going to dress down.”

It is clear on meeting them that their Boosh characters Vince Noir (Fielding), the narcissistic extrovert, and Howard Moon (Barratt), the serious, socially awkward jazz obsessive, are comic exaggerations of their own personalities. At the afternoon photo shoot, Fielding breaks free of the hair and make-up lady, sprays most of a can of Elnett on to his Bolan feather-cut and teases it to his satisfaction. Very Vince. “It is an art-life crossover,” says Barratt.

At 40, five years older than Fielding, Barratt exhibits the profound weariness of a man trying to balance a five-month national tour with new-fatherhood. After every Saturday night show he returns home to his 18-month-old twins, Arthur and Walter, and his partner Julia Davis (the creator-star of Nighty Night) and today he was up at 5am pushing a pram on Hampstead Heath before taking the train north to rejoin the Boosh. “I go back so the boys remember who I am. But it’s harder to leave them every time,” he says. “It is totally schizophrenic, totally opposite mental states: all this self-obsession and then them.”

About two nights a week on tour, Fielding doesn’t go to bed, parties through the night and performs the next evening having not slept at all. Barratt often retreats to his room to plough through box sets of The Wire. “It’s a bit gritty, but that is in itself an escape, because what we do is so fantastical.”

But mostly it is hard to resist the instant party provided by a large cast, crew and band. Indeed, drinking with them, it appears Fielding and Barratt are but the most famous members of a close collective of artists, musicians and old mates. Fielding’s brother Michael, who previously worked in a bowling alley, plays Naboo the shaman. “He is late every single day,” complains Noel. “He’s mad and useless, but I’m quite protective of him, quite parental.” Michael is always arguing with Bollo the gorilla, aka Fielding’s best mate, Dave Brown, a graphic artist relieved to remove his costume – “It’s so hot in there I fear I may never father children” – to design the Boosh book. One of the lighting crew worked as male nanny to Barratt’s twins and was in Michael’s class at school: “The first time I met you,” he says to Noel, “you gave me a dead arm.” “You were 9,” Fielding replies. “And you were messing with my stuff.”

This gang aren’t hangers-on but the wellspring of the Boosh’s originality and its strange, homespun, degree-show aesthetic: a character called Mr Susan is made out of chamois leathers, the Hitcher has a giant Polo Mint for an eye. When they need a tour poster they ignore the promoter’s suggestions and call in their old mate, Nige.

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