Ask anyone who knows him and they will tell you that the multitalented Mark Ronson is a little bit nerdy. His habit of showing up for DJ gigs with countless crates of records and truckloads of techno kit sets eyeballs rolling. He’s also a mite showbiz — apparently, he had an enormous absinthe jelly in the shape of St Paul’s cathedral at his birthday party. At the same “come as your favourite album cover” party, a music-industry friend bemoaned the fact that there wasn’t an album called Name-Dropper, as then he could come as Mark and go around dropping Post-It notes with names written on them, such as Amy Winehouse, Jay-Z, Puffy and Tom Cruise, as well as the many others he unashamedly counts among his acquaintances.

So when Ronson lets down a crew of nine people who show up to photograph him for Style with his latest discovery, Daniel Merriweather, I’m ready to loathe. His management insists he is ill, but the morning’s papers show him rolling round London in the early hours with several women who are least likely to have an early night — Lady GaGa, Miquita Oliver, Lily Allen and Kate Moss. “That Kate Moss is good for nothing,” says a furious Merriweather. “Like, where’s our boy?”

Merriweather is an Australian with some extremely misspent teenage years as a red-neck hardnut on the wrong side of the tracks in Melbourne. It’s a history that you might not immediately suspect when you listen to his emotionally charged, Ronson-refined hits such as Stop Me, Change and Chainsaw. But unlike Ronson’s other friends and collaborators, Winehouse and Allen, Merriweather is no lash-batting pop princess.

Ask him where he got the scar on his cheek, and he won’t hold back. “In a fight when I was 18.” He describes how his friend “Die Hard” suggested field surgery on the flap of skin hanging off his face so they wouldn’t have to face the authorities. “I’d never have a fight now, I’m a grown-up. But when I see Mark tonight there’ll be a fight.”

“Yeah, I had a big night,” says Ronson a few days later, “but I did call at 7am to say I wouldn’t make it. My manager tried to save face, so I felt an idiot knowing there were pictures out there. It’s like when management say, ‘Amy’s been rushed to hospital for exhaustion.’ It’s embarrassing.” He says he had been doing “that whole not drinking thing”, but after a day in the studio working with Lady GaGa, they went on a bender. And the rock’n’roll offence is instantly dispatched with a dash of easy, geeky charm.

Ronson is obviously great with women, collecting impressive girlfriends, from the actress Rashida Jones, the Harvard-educated daughter of Quincy, to scrummy, smart models Frankie Rayder and Daisy Lowe. Currently it’s Tennessee Thomas, the drummer with the Like and “the most entertaining woman I know”, according to Alexa Chung. Mention Chung’s praise to Ronson and he says: “That sounds about right. Then again, I’ve heard Barbra Streisand is supposed to be pretty funny.”

Ronson comes from a big, powerful, British Jewish family — Uncle Gerald was involved in the Guinness scandal back in the 1980s. His tastefully preserved, Odeon-heiress mother, Ann Dexter-Jones, is ferociously social. Everyone is A list, even the teenage half-siblings. His mate Lily Allen apparently got on so famously with his sister Sam’s girlfriend, Lindsay Lohan, that the pair are going to make a record together.

For Ronson, all this is accident, not design. What redeems him from the rich-brat label is his actions, which speak far louder than any family tree. When Merriweather first came to New York, aged 20, to start working with Ronson, he slept on a futon in Ronson’s one-bed loft for months. Similarly, Ronson flew Allen — then just his mate’s nobody gobby girlfriend — over on his Air Miles to work on the tracks that ended up on her first album.

Merriweather was one of the first artists Ronson signed to his Allido label, and it’s taken five years for them to get the forthcoming album, Love and War, off the ground. Ronson recalls getting ready with Merriweather “to go to Puffy’s white party in the Hamptons”. The pair were running round H&M trying to find the kid from the wrong side of the tracks a suitably smooth outfit. “I said, ‘Dan, now you’ve got to understand — and I know this is something you’ve never done before — but if you get angry, you just walk away.’ ” I wonder if that wasn’t patronising. “No, it was big-brotherly. I wasn’t anybody at the time, I hadn’t even had a record out. Dan’s been there with me the whole way.”

Unlike many privileged offspring, it’s Ronson’s skills and not his connections that have got him places. It’s unlikely his socialite mummy helped him 12 years ago, when “Puff, Jay and Biggie” came down to his hip-hop nights in grimy Lower East Side clubs. “Probably because it was a bit exotic, a mix of hustlers, hip-hop fans, skatecore, drug dealers” says Ronson, and happened to be run by “a gangly 23-year-old nobody white kid. I got the authentic hip-hop nod because I was good at what I did”.

Puffy subsequently asked Ronson to be an A&R for his Bad Boy label. “I was incredibly flattered, but I wasn’t ready to take it on, I was happy just DJing at that time.” Similarly, he understates his connections with Jay-Z. “When we occasionally have chats about the future of music, it’s like sitting down with the Pope or the president.” And when his — now, very good — friend Q-Tip first left a message on his answering machine, “I geeked out and invited all my friends round to listen”.

Unspoilt by his much-hyped connections and the orbiting A-list swank he encounters, Ronson comes across as a sweet-natured music geek. He might be surrounded by stars, but he’s for real. “I don’t want to ever lose that part of me that makes me a fan.”

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