Big Robbie Coltrane is up for all Potter films even though he still thinks kids are “smelly, selfish, squealing, little brats”.

It's the world premiere of Harry Potter and the Prisoner of Azkaban, and Robbie Coltrane is knackered.

"I'd forgotten how exhausting these things are," says Coltrane, referring to the massive press junket process that goes along with a Harry Potter blockbuster.

"It's really like being a liar, you know, and you have to be careful when you're a liar. You ask yourself, 'Have I spoken about this to these people before, and am I going to get 40 eyes going: we've heard this big boy?'"

Coltrane is dressed all in black, and despite our New York hotel setting, insists on smoking a cigarette as we talk, initially about the blockbuster franchise that has changed his life, professionally at least. Perhaps, he muses, he may never have embarked on the Potter films had it not been for recent fatherhood.

"I don't think I could have done Hagrid before I had my children, because I didn't really like children," says Coltrane.

"When you're in your twenties and thirties and you don't have children, they just seem like smelly, selfish, squealing, little brats, which of course they are."

But Coltrane's children, one eleven and the other six, seem quite, well, they're quite "cool with" the notion that their dad is playing Hagrid.

"They don't think there's anything peculiar about seeing their dad on the screen as that's what their dad does, you know. What you don't see til you're a parent, I suspect, and this is my own experience, is all their wonderful redeeming features."

While Coltrane says that he as grown, more as a parent than an actor, since the beginning of the Potter films, he marvels at the growth of the three children who are the leads in the films, namely Daniel Radcliffe, Emily Watson and Rupert Grint.

"Their concentration is much more casual then it used to be. They used to be kind of: Well I'm going to do something difficult in 10 minutes so I'll get prepared now, whereas now they just kind of all muck around on the set and tell jokes like old actors do. They're much more secure, and more certain of what they can do."

Coltrane knows what he is talking about. After all, the heavy-set Scottish actor has appeared in over 60 films, as well as numerous TV series, especially Cracker, which garnered him new found popularity and respect. Yet looking back, Coltrane finds little to miss about his tellyvision days.

"I don't miss the schedules, which were just horrific, not compared with the American ones, but then they get a few extra zeros on the end in their wage packets. Also, I don't miss that level of recognition you get when you're on TV," adds Coltrane.

"There's a kind of terrible lack of respect from people if you do telly, because they think you're a part of the family, and that it's all right to come and sit on your knee in the middle of an airport. The worst thing about doing telly is that the people who come up to you when you do telly are almost invariably arseholes," says Coltrane.

"And they are arseholes at their work, they're arseholes in the pub, they're probably the arsehole of the family and if you're related to them you think, oh god, here's Uncle Jim, and he's an arsehole. He will be the guy who comes up at the airport and decides to sit down beside you and show you his maps and binoculars and wonder why you're annoyed, you know? Whereas, everyone else in the airport recognises you but thinks, leave him alone, he's having his life."

They are, he says, different from the multitude of fans he has since inherited since working on the Harry Potter films. "They're not as crazy as you'd think." Not even the children. "Their parents like to tell them who I am, though, because they get brownie points you see," he adds with a sly grin.

When Coltrane isn't busy donning thick beards and Hagrid make-up, the actor can be seen in the series finale of Frasier, which is yet to air outside of North America, where he played one of Daphne's brothers, a mumbling drunk. Coltrane considered it an honour to be a part of American television history.

"It was an hour long and I was only on for two minutes," he says modestly. "They'd asked me to do it before and I never could, because of other things. They're kind of fans of Cracker, they know my work and of course they can have who they like, because they're such a successful show."

Coltrane is now preparing for the fourth film, and possibly the last with the current trio of kids, but as for Coltrane, he has no idea how much longer he'll be working on this franchise. But he does know why the Harry Potter films have proven so successful as they continue to become entrenched in our popular culture.

"All great works of art are about what human beings are really like. When I was ten, all literature was about white people conquering Africa and fighting the Germans. There was absolutely no kind of psychological insight into what was actually going on in my life."

He recalls being brought up on the diverse likes of The Lone Ranger, Ivanhoe and Phil Silvers, all of which collectively influenced Coltrane's life. As for comedy, the late British legend Tony Hancock was another huge influence.

"In terms of subtlety he was on the same level as The Office. Now 20 years ago no-one would have got The Office here because irony had not been rediscovered. There was a whole gap in American history where irony just went on holidays. I tell you, Steve Martin was one of the only great ironists that really made it. Irony kind of disappeared from American comedy for about 15 years and now, I mean you don't get any more ironic than Frasier do you? My god, the whole thing is about irony isn't it?"

There may be nothing ironic about Harry Potter, but at least the film has in some ways reinvented Robbie Coltrane, for better or worse. Coltrane's next big problem is getting his teeth into Harry Potter and the Goblet of Fire.

"The script isn't finished and they can't give you a schedule until they've worked it out. The trouble with four is working out what to leave out. It should really be 2 movies and everyone says you can't do that. Remember Kill Bill?"