Richard Hammond is talking quickly and in capital letters. He has his heart set on a De Tomaso Pantera sports car about to go under the hammer at Bonhams when we meet at Century Club in central London.

"Oh God. It's perfect. It's ludicrous. Mid-engine like a Ferrari, like a Lamborghini, but it's a massive Cleveland V8. I'm CONSUMED, CONVULSED with lust for it. I want it. DESPERATELY." His voice turns to a conspiratorial whisper as he plots the purchase, before adding, "My daughters will HAATE it."

One third of the triumvirate that makes up the BBC hit show Top Gear, Hammond says he's "had a bit of a thin-down" when I ask how many cars he has. He owns 28 bikes and "probably 10 cars, maybe more". Some thin-down.

Cars, he explains, still make him feel funny in his tummy. "You can intellectualise it, of course, but I love them because they excite me, I love the way they make me feel. It's visceral and basic."

Hammond, 43, has just written his autobiography, tracing his journey from childhood in the West Midlands to early adulthood.

He apologises now for the reckless driving of his younger years which he attributes to the "impossible arrogance and sense of immortality" of being 17.

"It wasn't aggression in the sense that I wanted to hurt anyone. I would have been MORTIFIED if I'd killed anyone - which I could very easily have done. But that hormonal surge - there's nothing you can do about it. You're proving yourself, challenging yourself, challenging the world."

The challenges, of course, did not end with adolescence. Nor did the risk-taking. In September 2006, aged 36, he suffered a serious head injury and brain damage on a Top Gear shoot, having crashed a dragster-style car capable of reaching 480km/h. He remained off screen, recuperating, until the end of the year.

Seven years on, he's not aware of any lingering effects. The crash is "catalogued on my list of big experiences as we all have in our lives". His memory of childhood, he insists, is still intact. "If anything, the crash dislodged a lot of the rubbish that had been laid down on top of it."

Known to fans as "The Hamster", Hammond was born in Shirley, West Midlands.

The family moved to North Yorkshire when he was 15 and he was "booted out" of Ripon Grammar School. He went instead to art and technical college. The autobiography ends aged 21 on what he describes now as a rather celebratory note.

"But then I spent the next 10 years slogging away in local radio and missed out on a lot of fun."

As a 5-year-old Hammond sat down with his dad and worked out how many days it was until he could drive a car. When he interviewed a motoring correspondent on Radio Lancashire he knew he wanted to combine two favourites - cars and broadcasting. After a year and a half in PR he gave up the company car, took in a lodger and got a job in TV making motoring shows.

Eventually he auditioned for Top Gear. Months went by and he gave up hope. Then, the phone went. On hearing the news, he burst into tears before ringing back: "Did you mean me? Richard Hammond, the short bloke?" He told his wife, Mindy, "This will change everything." And it did.

Top Gear is a worldwide hit. "We've been filming in Ukraine - we couldn't get out of our hotel in the morning for fans."

Next the show will feature a trip to Burma.

Success has also been a passport to presenting natural history programmes. He recently picked up a Jackson Hole Wildlife Film Festival award for presenting Miracles of Nature: Super-Bodies.

So does he ask himself whether making a programme celebrating cars is the right thing to be doing environmentally?

"No, honestly, honestly, no ... The ability to move ourselves about, that's fundamental, humans need it. The inevitability of then turning that into something competitive and flamboyant is also quintessentially human.

"A handful of freight ships create as much carbon monoxide in a year as all the cars in the world put together. How much fuel do we burn in our homes when we could put on an extra jumper?"

Jeremy Clarkson was already long established on Top Gear when Hammond signed up to the revamped version 11 years ago. James May rejoined the programme a year later. Is he friends with them?

"I must be. We spend more time with one another than we spend with anybody else and we haven't actually stabbed each other yet."

•On the Road: Growing up in Eight Journeys - My Early Years by Richard Hammond.

- Daily Telegraph UK