'There was an advert in the local paper – an Italian man was selling an entire fleet of them and I couldn’t resist. It looked so beautiful: half pink, half cream with a blue roof, fibreglass body and wings at the back.

‘I remember the first time I took it out around my neighbourhood. I pulled in to the pub to do a U-turn and there were eight kids with their pocket money out, hoping to buy a choc-ice or whatever. But I had nothing to give them. I’ve learnt my lesson since then. These days I keep it well stocked. I probably spend more time driving around in that van than anything else, and if the acting suddenly comes to a halt, I can’t imagine a better job than being an ice-cream man. I love going on eBay and buying accessories for the van, things like light-up cones that I’ve stuck on the front. ’

I’m into arcade machines – I’ve got a Sega Rally 2 Twin machine and one of those coin-operated fortune-telling machines you see at fairgrounds. I’m really into my vehicles too. When Harry Potter started, one of the first things I treated myself to was a quad bike.

'Then I went and bought a hovercraft a couple of years ago. I just thought it would be a fun thing to own. If I’m not driving it around the lake in my garden, I’m out in the fields with it. I love golf so I’ve got a Hummer-style cart to get me round the course. It doesn’t improve my golf, though – I’ve been stuck on a 12 handicap for too long now.

‘My first car was an Mk 1 Mini, which I bought as soon as I could drive. I turned it into something of a chav car with Lamborghini doors, spinner wheels and lights underneath. Next was a 1950 Chevy pick-up in maroon and black. Very cool. More recently I bought a bright orange Range Rover Sport, which I get a lot of stick for. People rib me that I only bought it because it matches my hair.

'I wouldn’t mind a collection of old Mustangs and a few classic hot rods.’

‘That was never going to happen to me. Filming Potter is so intensive it doesn’t leave much time for going off the rails. It doesn’t mean that I can’t let my hair down from time to time. I never get completely out of my head but I can put away quite a few (drinks). But I’m aware, especially at premiere parties, that I can’t afford to be seen falling on pavements. I tend to do my drinking with old schoolfriends around the pubs where I live, rather than at glitzy showbiz places.

‘And I was never the kind of kid who was destined for trouble. Probably the worst thing I did was steal a hairbrush and a Billy Goats Gruff book from a local shop. I think I went in with the intention of nicking something and I must have panicked and grabbed the first two things I saw. Clearly a life of crime wasn’t for me.’

‘Rob didn’t have a big role in the film but I got to know him well,’ says Grint.

‘Everyone on the set liked him. He was a funny lad, a proper character. Going to his funeral... that was a sad day. Rob was the first young person I knew who’d died. The enormity of his death hasn’t really sunk in for me yet. But I’ve learnt something from it in terms of counting my blessings, realising how lucky I am and the importance of making the right decisions for the future.’

‘I’m not easily impressed by famous people, but nothing’s matched this,’ he says. ‘I didn’t think I was going to be nervous, then this huge motorcade pulled up at the studio and Michelle stepped out of a black Range Rover and everybody was speechless. It’s hard to imagine Gordon Brown having that kind of effect.

‘We sat around, ate cake and chatted. She said that the President is a big fan of the films and loves the books, and that she’d met the Queen the day before – but visiting the Potter set was far more exciting, that we were a lot cooler. It was hard to take it all in. I kept thinking, “Here I am talking to the First Lady.”’

‘The best thing about that was learning how to handle guns,’ he says. ‘We were at a shooting range, and I thought it would be easy. Just aim and fire, right?

'But it’s one of the hardest things I’ve ever done. I wasn’t prepared for how powerful and loud a gun is. When you fire, it physically knocks you back. But I did learn to take a 9mm Glock handgun apart and put it back together again blindfolded.’

Next up is the gritty thriller Cherrybomb, in which Grint stars as a troubled youth dabbling in sex, drugs and violence. ‘I don’t have a problem with violence in movies,’ he says.

‘I don’t buy into the idea that violence in films is responsible for knife crime and things like that. Most people can tell the difference between a film and real life. I’m a huge Tarantino fan – I love Reservoir Dogs and Kill Bill, and if he came calling and offered me a role, I’d take it.