When Matt Berry was a little boy growing up in Bedford, his parents left an organ in his bedroom one night. Not a severed ear or a still-beating heart, but the kind with a keyboard. “They never said anything,” says Berry. “There was no explanation, no lessons, just me and the organ.”

In short order, he had mastered the keyboard, then the guitar, and soon his big goal as a teenager was to emulate multi-instrumentalist Mike Oldfield. “I read that he was 17 when he made Tubular Bells. I thought, ‘I’m 14 – better get a move on.’ That’s what led me to buy a secondhand bass guitar and a four-track recorder.”

This isn’t what I expected at all, the revelations of a self-taught polymath. I’d hoped to conduct this interview from two open-top sightseeing buses. Berry would be on one and I’d shout questions through a megaphone from the other. This would have been a reprise of the bus-off between his most famous creation, the eponymous thespian lothario from TV comedy Toast of London, and that character’s turtle-necked nemesis, Ray Purchase. “Everyone in London knows your wife’s a prostitute,” shouted Toast . “You take that back, Toast,” retorted Purchase.

Instead, we’re reclining on a leather sofa in a Soho club. Berry is sipping Diet Coke. Again, this is intolerable. The 45-year-old should be importuning waitresses, channelling the role of Douglas Renholm, the lecherous boss he played in The IT Crowd, running about shouting: “God damn these electric sex pants!” Or he could even be drinking the bar dry, like his latest TV incarnation: mutton-chopped, one-eyebrowed, foul-mouthed Victorian detective, Rabbit.

Don’t mess with the mutton-chop … Berry with Susan Wokoma in Year of the Rabbit. Photograph: Sam Taylor/Objective/Channel 4

But, no, Berry’s detailing his teenage recording techniques in a hushed voice. He is amiable but, and there’s no easy way to say this, shy and sartorially uninteresting. Yet I’m grateful for the organ story since it gives a rare insight into Berry’s past. He scarcely mentions his upbringing or private life in interviews. “I’m a clown,” he says. “That’s what everybody wants me to be. Nobody wants to hear about my ‘psychic wound’. Nobody wants me to be their life coach.”

What nonsense. Matt Berry Was My Life Coach – what a movie that would be. But he has a point. If we knew the dreary truth about Berry, that would ruin the fantasy. We want to imagine him as Toast, flatsharing with a similarly bitter thesp. As for psychic wounds, well, we inch closer to one when Berry tells me about his first day at Nottingham Trent University. It was there he studied contemporary art and dreamed of becoming a painter.

“A lecturer stood up and said, ‘Here are six paintings. Which is the odd one out?’ Then he pointed to one and said, ‘It’s this one. Because it’s the last painting I ever did.’ I admired him for saying that. It was an epiphany for me. I realised I didn’t want to make the mistake of getting a proper job. I wanted to do art for ever.”

Playing Jack the Ripper at the London Dungeon for £178 a week wasn't Rada – but you learned not to fluff your lines

It didn’t quite work out that way. After graduating, he made for London and slipped into miserable positions in telesales before landing a job at the London Dungeon. He was paid £178 a week to play a judge in the morning and Jack the Ripper in the afternoon. “It wasn’t Rada, but you learned how to get the story right and not to fluff your lines.”

Then, in around 1999, he met Noel Fielding. Like Berry, the Bake-Off host and funnyman has art chops and no formal training in acting. They clicked and Fielding invited Berry to perform some songs at Islington’s Hen and Chickens pub. “I was doing serial-killer confessionals in song: ‘This is where they bodies are buried!’ I thought they were funny.”

On the same bill were Richard Ayoade and Matthew Holness, who persuaded Berry to star in their parody of 80s horror TV, Garth Marenghi’s Darkplace. Full of dodgy acting, choppy editing and flawed storylines, all of them deliberate, the show aired on Channel 4 in 2004, giving us the first taste of the rich, fruity voice that has become Berry’s trademark.

Thespian lothario … Berry with Tracy-Ann Oberman in Toast of London. Photograph: Channel 4

Since then, he hasn’t stopped. He paints, acts and has released six studio albums, even writing – with Ayoade – a satirical rock opera called AD/BC. Music, he says, is the most important outlet for his creativity. “I dream about music, never comedy.” How? “Well, I dream of guitars – different kinds of guitar.”

Earlier this year, Berry starred as Michael Squeamish, a know-nothing TV hack, in a mockumentary called The Road to Brexit, co-written with longtime collaborator Arthur Mathews. “I thought it was funny, a breathing space from the madness.” Did researching it change the way you vote? He laughs, by way of an answer. “I don’t want to say.” Why? “Because I don’t want to be anybody’s life coach.” Again with the life coach.

And now there’s Year of the Rabbit, a Channel 4 show starting next week in which Berry plays a liver-ruining detective battling Victorian London’s parade of nonces, ponces, top-hatted tossers, pre-pubescent narks and post-menopausal booze slingers. Rabbit (his sister is called Weasel, his brother Leopard) is a swearing virtuoso. Legend has it, I tell Berry, that sellers at London’s Billingsgate market could swear 20 minutes straight without repetition. We have lost that art: now swearing is reduced to Gordon Ramsay effing and jeffing on autopilot on Kitchen Nightmares.

Year of the Rabbit has a working-class warmth you don't see convincingly elsewhere

“That verbal creativity is what I like about Rabbit” says Berry. “There’s a lot of my dad in the role. He has that dry deprecatory wit. If I was going to do something stupid, he’d say, ‘Oh, going to do that, are you?’ I wanted to capture that British deflationary way of speaking.”

Rabbit is assisted by rookie Wilbur Strauss, a Cambridge criminology graduate played by Freddie Fox, and his adoptive daughter Mabel Wisbech, portrayed by the droll Susan Wokoma, who is striving to break Victorian policing’s glass ceiling. Together this threesome fight a losing battle against crime. “It’s the Victorian Sweeney,” says Berry. How would he know? Berry for many years didn’t have a TV. “Well, I was too young to watch The Sweeney when it was first on, but I caught up with it fairly recently. I’ve become quite obsessed.”

Berry wants Year of the Rabbit to echo Only Fools and Horses, John Sullivan’s classic London sitcom, in one respect. “It has a working-class warmth that you don’t often see convincingly elsewhere. I got it from my dad and my grandmother – that warmth and fondness coming through in sarcasm.

“In Year of the Rabbit, I wanted to get the rookie-cop-and-old-hand cliche done and dusted fast. We’ve seen that a million times. What I wanted to get to was the sense of the three of them looking out for each other – even as they rip the crap out of each other.”

Swearing masterclass … Year of the Rabbit. Photograph: Sam Taylor/CHANNEL 4

One lovely moment has Rabbit explaining his beat. “This city is a rat eating its own babies, babies made of shit, and once it eats its own shit babies, it shits them out again, and then it noshes them, and that goes on and on until the sun turns cold and the sea goes back into the sky.” Which is of course exactly the sort of briefing Met boss Cressida Dick wishes she could make.

Year of the Rabbit could be the unexpected comedy delight of 2019. Equally welcome news is the fact that Berry is planning a fourth series of Toast of London. He’s just not sure when he’ll have time to write it. For three and a half months a year, he’s now contracted to live and work in the US, filming What We Do In the Shadows, the comedy horror series about four vampires rooming together in New York.

Why play Toast again? “Because he’s the anti-me. I wrote him because I met so many actors who are utterly vicious about other actors – always frustrated, bitter and cynical. I’m not. I’m doing all the things I ever wanted. More than I ever imagined. I never dreamed of being a comedian. I never imagined I’d be a clown. There aren’t enough hours in the day. But otherwise I’m living the life I wanted.”

What about doing voices for ads? Surely they’ve made you rich but not creatively fulfilled? He laughs. “I’m amazed I still get the work.” Why? “I thought I’d satirised the job into oblivion as Toast. But that only made them want me more. Weird.”

• Year of the Rabbit begins on Channel 4 on 10 June.