Why leave behind a promising music career as a big fish in British hip-hop, which includes releasing three albums and performing with Mos Def and Kanye West, and start from scratch on the comedy circuit?
Doc Brown, real name Ben Smith, brother of novelist Zadie, has heard the question before: "Sometimes I get attacked by my fans online for that. It's exactly the same question they ask me. It's like I woke up one morning and said, 'Right, forget music now, I am going to try and be a stand up.' The whole thing happened so organically, comedy took all of my creative time and my mental space."
Smith's transition to comedy started four years ago at the time of his first album when work on voiceovers and jingles for Radio 1 led to contributions for Oneclick/comedy, formerly The Milk Run and a place where a lot of new comedy talent has passed through. "I was so serious about my music that I said to them that I didn't even want my name on it. But then I had this feeling that retired footballers must have when they have played in front of 60,000 people and all of a sudden are sitting silently in their houses. I didn't think about quitting but I was thinking how much further could I take rap, a niche art form in Britain."
Smith then managed to get to the finals of a comedy competition in Edinburgh after the heats in London and comedy has been his métier ever since. He says that his music was always liberally sprinkled with humour and anyone who has read his sister's New Yorker piece, "Dead Man Laughing", knows how comedy was at a premium in the Smith household, principally because of their father: "Dad was a big influence. He was very funny in a tragic British way and he loved to wallow in self-pity. He was a great moaner, a great worrier but a great one-line maker. He got me watching comedy, among the first shows were Monty Python, whose sketches me and my sister used to act out, the Marx Brothers and Harold Lloyd. He even had me watching Reggie Perrin when I was 10, which was way too old for me."
In her essay, Zadie Smith talks most about Fawlty Towers as that was the bind between her and her father but for Ben Smith it was Porridge: "We liked the mainstream stuff as well like The Good Life and Porridge, which was my favourite. There's one episode called "A Night In" that sticks in my mind because of its ability to put comedy and poignancy together. While my dad was a real old-school white working-class south Londoner my mum was a young Jamaican immigrant into soul and reggae and black comics like Richard Pryor and Eddie Murphy and she introduced me to both of them and I started to realise that comedy and poignancy could be conveyed in stand-up too."
Smith family life is described as one where creativity and enjoyment was encouraged and where there was a "love of music, of lyricism and lines and turns of phrase."
Smith, of course, is aware of how much his background has been scrutinised because of the fame of his sister and without specific prompting gets to grips with the context of what his sister called "social fluidity" when talking about her own background and the background to the story of her best-seller White Teeth.
"Just because we grew up on a council estate that doesn't temper anything we do. We're not saying that we are working-class heroes and that we are more successful in a way. I never felt poor, ever. Our parents were working-class people who had very middle-class sensibilities in their approach to parenthood and experience of childhood. My mum would do things like go to a little patch of grass and dig until we got to some clay and then we'd make stuff out of it. I don't see a lot of workingclass mums taking time out to do that kind of thing. It's a small thing but it really sums up what our childhood was like."
Watch Doc Brown's video 'Hood Sportz: Volume One'
Having a more famous sister meanwhile is something Smith is apparently equally relaxed about and a connection that is openly flagged up in his press material: "What's the point of not being up front? If we were both novelists you'd probably be sitting in front of a bitter and twisted individual. But, while we both write, we do very different things and there's literally no competition. I'm her biggest fan. She's a huge comedy fan but would never stand on stage and tell jokes. We support each other. It was more difficult back in 2001 when she was massive and I was a hardcore rapper and I had people were coming up to me and saying, "I've heard your sister's posh.'"
Smith says he could see his sister's success as inevitable, recalling her attempting to write a novel on the typewriter when she was 12.
And it was his sister that first got him into hip-hop, but while there was bonding over music as youngsters, Smith's subsequent path change to comedy has bridged the gaps that formed since his sister went to live in New York while his younger brother, Luc Skyz, 26 [Zadie is 33 and Ben is 31], is pursuing a career in rap.
Smith spent a lot of his time at university putting on parties, which must have nurtured his future music career but to some degree he laments his hedonistic student lifestyle, remarking that the University of East Anglia wasn't perhaps as conducive to study as Cambridge where his sister was living in E M Forster's old room.
Initially, Smith followed a performing arts course but was somewhat put off by the lecturer who, at the end of his first term, forced his idea on the group for their end of year show; a piece about the draining of the Fens in the 1600s where Smith was pre-cast as a slave. Smith left UEA but returned after balking at the prospect of paying rent at home and signed on to social sciences ("I still don't know what that is" he says) where his mixed-race background again came up as an issue.
"I followed courses in multiculturalism and black history. I was the only black guy in the class and after one lecture I remember the lecturer asking, 'What did you think?' and stuff like, 'How do you think Martin Luther King would have felt?' I said, 'Dude, I'm just black, you're a published professor, I don't know!' If I cleared my throat during a lecture people would be like, 'He's going to say something, some piece of black intelligentsia.'"
Now in his role at the head of the group, albeit as jester rather than lecturer, Smith is still fighting shy of the self-consciousness of others: "I won't do racial jokes, I won't pander to either black or white audiences. I've been accused of not being black enough already but I'm the blackest comedian out right now. I never talk about politics. I'm not well informed enough. It's my personal politics I talk about, about being mixed race in the multicultural world around me."
He's excited about going to Edinburgh, and one of the reasons is that the Fringe is the antithesis to the cool-obsessed music industry as he saw it: "They don't care if you're ugly, fat, old, black white... in fact, the uglier and fatter you are the funnier you probably are."
Doc Brown: The Comedy Reserve, Pleasance JackDome, 5-31 August, 9.30pm (not 18 and 25) (0131-556 6550; www.pleasance.co.uk ). Watch Doc Brown's video 'Hood Sportz: Volume One' at www.independent.co.uk/arts