Graham Norton doesn’t mind being called camp. Following in the mincing footsteps of John Inman through Julian Clary, his blend of bitchy humour and waspish put-downs has made him a celebrity.

But when not in front of the cameras his personality takes a turn for the butch. In fact behind the wheel of a car you could easily mistake him for a white van man.

“I drive around shouting and swearing a lot,” he says. “I’m a real Mr Angry as soon as I get in my car. I only learnt to drive five years ago and I have no idea what I was doing with all my bottled-up anger before then.

“It’s good that I’ve got such an outlet for it now, but when I have people in the car with me they say it’s as if I have become a different person. It’s totally unconscious, but I change.”

The first car that Norton bought backs up the impression of him as an aggressive driver: a Porsche Cayenne. This is probably the ugliest and most intimidating of all the large 4x4s on the road, and although Norton passed his test first time he now admits that buying it was probably a mistake.

“It was like driving a truck,” he says. “On reflection it was not the best choice of car for a newly qualified driver. I’ve never had a car crash but I certainly bounced all over the multi-storey car park in it.

“I got a bit impatient trying to get out of a tight squeeze on one occasion and I had a scrape that left part of the car there. It was a pointless bit of car and I don’t know what it did — it was just under the headlight and I didn’t even notice it had gone for two days.”

He could probably afford the repair bill. Since bursting onto the scene in 1998 with his Channel 4 chat show So Graham Norton and its successor V Graham Norton, his blend of innuendo-laden humour and graphic shock tactics has punctured the pomposity of dozens of celebrity guests and in the process made him a millionaire.

Three years ago he was poached by the BBC for a figure reported to be in excess of £3m, where after a brief lull he has recently flourished as the host of How Do You Solve a Problem Like Maria?, in which Andrew Lloyd Webber tried to find a lead actress for his West End version of The Sound of Music, and its follow up Any Dream Will Do.

Born Graham Walker in Clondalkin, on the outskirts of Dublin, Norton had a father, Billy, who was a Guinness sales rep — a job that meant the family had to move home frequently. They eventually settled in Co Cork, where he grew up as part of the republic’s minority Protestant community.

In his autobiography So Me he remembers dressing up in his sister’s clothes and noted that it was “easier to be gay than Protestant in Ireland”. Norton attended Bandon grammar school in Cork then moved to London and trained at the Central School of Speech and Drama alongside future film stars such as Jason Isaacs and Rufus Sewell.

He soon realised he would never fulfil his dream of being a serious actor and drifted into waiting tables while performing on the stand-up comedy circuit.

Today his plush apartment in east London overlooks the River Thames. The tight entrance to the development and the small parking spaces are some of the reasons he sold the massive Porsche, opting for a smaller Lexus SC 430.

He says he was seduced by the sporty looks and the clever hard-top folding roof. But while the car may have made reverse parking easier it had an even more serious drawback: there was no space for Norton’s new dog (a cross between a labrador and a poodle called Bailey).

So he’s had to upshift again, this time to a Lexus RX 400h, the hybrid 4x4 that is congestion charge exempt and if driven below 15mph runs entirely on its electric motors. “It’s more like a regular car, which makes me slightly suspicious about how environmentally friendly it really is. Then again I’ve only had it a few weeks but I have just used a single tank of petrol, whereas in my old car I was filling up every few days,” he says.

“Clearly driving a hybrid car is not going to save the planet. But it’s very easy to find reasons to do nothing and sit on your arse. This is not as damaging as driving a regular vehicle and that’s what persuaded me to buy it. On balance it’s better to do what you can, I think.”

He doesn’t regret rejecting greener motoring options. “I test-drove a Toyota Prius but that was too much like driving a milk float,” he says. “Then I thought briefly about the G-Wiz, but I think I would look like Postman Pat in one of those.”

Whether he is any more successful at negotiating tight parking spaces in the Lexus RX 400h than he was in the Porsche remains to be seen but at least he’s proving his environmental credentials.

Eager to justify his renewed £5m contract, the BBC has cast him in David Attenborough’s latest campaigning wildlife series, Saving Planet Earth, due to be aired next month.

Each episode features a different well-known personality encountering endangered species. Norton ventures into the lair of Ethiopian wolves. Okay, it’s as much about being a jokey celebrity as planet saving, but Norton is doing what he can.

On his CD changer

In the glove box I’ve got the new album by Travis, The Boy With No Name, Overtones by Just Jack and Mark Ronson’s Version