Naughty Boy – sought out by Britney Spears, co-writer of Emeli Sandé's million-selling debut, author of summer dancefloor smash La La La ft. Sam Smith – is sliding around the back seat of a hackney carriage.

He’s heading home – to the house he still shares with his mum and dad in a humble terrace in Watford.

The 27-year-old producer-turned-artist is explaining he used to work in WH Smiths’ music department in the town’s identikit shopping centre, the Harlequin.

The role meant he could order import releases – Timbaland, Puff Daddy, American mid-noughties R’n’B – early, and at discount. It sounds like every teenager’s dream. Yet, he says, somewhat surprisingly, “I was working there for all wrong reasons.”

He did stints at Burger King – “I got sacked for being rubbish” – which sounds like quite a feat and, more recently, ferried Dominos pizzas round the Hertfordshire town. “That was my last actual job. I got sacked for taking too much time delivering. It once took me two hours. I suppose it was good to learn what’s not for me.”

Then came a slice of luck every young musician dreams of: £44,000, thanks to some savvy decision-making on Deal Or No Deal. He turned down the banker’s £35,000 offer and cashed out on his 26th episode back in 2005.

“The money gave me two and a half years of not working. It bought me time. To be honest, money can only give you time unless you want to put it in an investment. I wanted to invest in myself to become a musician. I wanted to understand how to make music on a computer.”

The windfall, combined with a £5,000 grant from The Prince’s Trust, set him on his way after he’d dropped out of London Metropolitan University.

He was scared – not least because his Pakistani parents wanted a young professional to emerge from the studies – but it helped spur him on.

“You can use that fear in two ways. You can give into it and do what is expected of you. But I had to do something a bit crazy, and going on a game show was a crazy thing I knew I could do if I tried. I had never seen it before so it’s not like I knew what to do.”

Now he’s heading out on his debut headline tour, taking centre-stage for the first time, his message is that there are no rules. Be honest with yourself and what you want because there is no blueprint for success.

He says the music bug came early. Shahid Khan, as he was born in 1985, remembers listening to the odd Elton John concert at Vicarage Road, Watford FC’s ground. He’d stand in a nearby street rather than inside the stadium because he couldn’t afford a ticket.

Back then, he shared a room with his sister Saira and the siblings used to join their father on weekly trips to Southall or Luton to buy Bollywood cassettes.

Other loves were Nitin Sawhney, as well as Nelson Mandela and Bob Marley for their quotes, which Khan used in his music.

“I remember there was a UN conference where a young girl read a speech and it was so moving I used it in a song. Words gave me more inspiration to make music.”

After successfully pitching tracks made as Naughty Boy to Chipmunk and Taio Cruz, he met Emeli Sandé at a showcase for unsigned artists.

“After being on the game show and getting help from The Prince’s Trust, I was more confident as a person. It wasn’t just about money, I needed these things as a person.

“Towards the end of 2008 I met Emeli. We were both unknowns, we had no managers or anything, and I was able to go up to her because I felt more confident. I was hoping she’d want to hear my music, which she did.”

After co-writing with Sandé, using some of the Deal Or No Deal cash to put her up in a B&B during sessions, he worked on records for Leona Lewis, Professor Green and Tinie Tempah in a studio he’d built himself in Enfield as a replacement for his parent’s shed.

As for his recent offer of working with Britney Spears, he says bureaucrats at the American Embassy stopped him jetting off to LA to write with her in person.

“I’ve got my visa now but it’s too late. The track I did with William Orbit is going to be on her record. If she wants to come to Watford, I’ll take her to Watford FC - not that I’m a hardcore fan. It’s a hometown thing.”

Friends picked up over the past few years – which he describes as being “like a film” – sing on the first record with his name on the cover, Hotel Cabana.

Sandé and Tinie Tempah are on Welcome To Cabana; Wretch 32 is on Pluto; Ed Sheeran is on Top Floor (Cabana), plus there’s Gabrielle, Bastille and George The Poet.

Chart success

But it’s the year’s fastest selling single, La La La ft Sam Smith, which transported Naughty Boy to the big league.

“It was the sample that got me going but I still didn’t think it was clubby. It’s an emotional song about getting your heart broken and not wanting to hear it. It’s nice that it did crossover and around the world it’s gone into top ten – I actually can’t believe that.”

New single Think About It sounds like Amy Winehouse meets Jay Z. The record has ballads, Bollywood, soul, two-step and could arguably be the sound of modern Britain.

“If modern Britain is a culmination of many different things then that’s true. You will hear on my album that this country is multicultural and diverse.”

There is soon to be a documentary aired on the BBC Asian Network about Khan, painting him as an idol for British Asians. Naughty Boy, somewhat worryingly, says only Simon Cowell has ever made him feel starstruck.

“Simon Cowell asked me to get involved with Leona Lewis and and invited me to his dressing room at Britain’s Got Talent. That was when my jaw dropped. Him saying Clown was one of his favourite songs ever, that opened my eyes.

I think he even called me a musical genius.”