Not only did she get up but she came back at him karate-style and nearly put his eye out. "Bruce wanted it gritty and real, so I gave it to him, " she explains. "I loved that. That's reality to me." Willis grins, ruefully. "I've never had my ass kicked by a woman in a film before, " he says.

They're filling me in on Willis's comeback as John McClane, the action hero he originated in 1988's Die Hard. After two sequels . . . the franchise catapulted him to fame, helping him become the sixth highest-grossing movie star ever with total earnings of over $2.5bn . . .

the fourth Die Hard now pits him against a cyber-geek terrorist who hacks into America's computer infrastructure, intent on shutting the entire country down.

"It would have been easy for us just to do CGI stunts, " he says.

After all, that's how blockbusters are now produced. Soon they'll be hard to distinguish from virtual reality video games . . . but not on Willis's watch. Die Hard 4.0 is a statement of intent. Whether with a patrol car zooming off a ramp to take out a helicopter gunship, or an SUV plunging down a lift-shaft while Willis slugs it out with Maggie Q, or a Harrier jet pursuing a giant truck beneath a collapsing freeway, digital trickery is kept to an absolute minimum throughout . . . and Willis has the bruises to prove it.

"For weeks when we were filming I was black-and-blue from the hip down, " he says. "I'd skin taken off me. I got knocked out once. I'd some stitches. It's like what they say about women and childbirth. If women remembered the pain of childbirth they'd just have one kid and that's it. I keep forgetting how much you get hurt doing this stuff. And at 52 it keeps getting tougher. I used to bounce off the concrete a lot easier than I do now."

Director Len Wiseman built massive stylised sets to create an actual space where the cast could be thrown wham bang into the thick of the action sequences instead of just miming performances before a blue screen. It pays off. No matter how over-the-top the chases, the crashes, the shootouts and the mayhem, there's always a vulnerable human presence that makes everything sardonically believable.

"I credit Len with bringing Die Hard into the 21st century and giving it a really smart shiny patina of technology but at the same time having the courage to do all the stunts, " says Willis.

"While we did have to do some CGI . . . because you're not allowed fly a jet down the streets of Washington DC . . . everything else is real in so far as anything is real in a movie. We threw a real car into a real helicopter. The car you see hurtling down a tunnel at me was on a sled that was on cables that made it spin and flip . . . and Maggie Q really does kick my ass."

Illiterate in computer technology, New York cop McClane is forced to team up with smart-ass hacker Matt Farrell . . .

played by 29-year-old Justin Long . . . to track down the elusive remote-control mastermind Thomas Gabriel (Timothy Olyphant) before he pulls the final catastrophic plug. It's inspired casting, a double act of opposites with echoes of Nick Nolte and Eddie Murphy in 48 Hours. Willis is ordered to bring Long to the FBI in Washington for questioning only to find that the bad guys for some reason want him dead.

"I don't do a lot of the crazy action, " says Long. "I'm usually on the sidelines cheering him on or wetting myself with fear. I'm kind of the mouthpiece for the audience, yelling 'Did you see that!'

as a car comes hurtling through the air and bounces off the roofs of two other cars on either side, leaving us unscathed."

While Long brings to Die Hard his persona as the unshaven, hoodie-wearing, hands-in-thepockets Mac guy he played in Apple's "I'm A Mac" advertising campaign, he's anything but an internet nerd.

"I had to fake it all, " he says. "I'm less technically savvy than most people of my generation. I actually relate a lot more to McClane's character in that I'm a bit oldfashioned. They had to brief me on all the technical jargon because a lot of the exposition comes through me. It's like speaking a foreign language. Five months ago I could tell you what a mutating encryption algorithm was. As soon as we finished shooting, it all left my head. It was the same way with math at school. I just don't have a mind for it. I can store very little up there."

Just as the original Die Hard was Willis's breakthrough, this fourth Die Hard could well be Long's. He first caught attention getting bashed about in Dodgeball and as a nervy smart-Alec in the indie movies Waiting andAccepted, but he's perhaps more familiar as the boyfriend who gets to kiss Britney Spears in Crossroads and Lindsay Lohan in Herbie Fully Loaded.

"Even my grandmother wanted to know what it was like to kiss Britney, " he says. "It was maniacal around the set, with bodyguards everywhere, but there's an element of absurdity to celebrity and all the publicity that feeds it.

When anyone comes up and recognises me I feel I'm letting them down somehow because I'm just a nerdy dude."

Long's father teaches philosophy at Fairfield University in Connecticut; his mother is the actress Wendy Lesniak.

"I grew up knowing that the reality of being an actor was not glamorous. It was fraught with a lot of heartache and rejection.

Mom did mainly theatre. She never had any delusion of grandeur when I got into the business. I always assumed it would be like that for me too, just doing plays and maybe by some miracle getting a guest spot on Law And Order or NYPD Blue.

"So every movie I do, even the crappy ones, it's been a surprise I've been allowed to do them. I keep thinking I'm going to get caught out, that someone is going to tap me on the shoulder and say, you know what, we've made a mistake. And if they did, I'd totally get it and be glad it's lasted this long and been such a fun run."

Perhaps this has something to do with being brought up a Catholic and educated by Jesuits. "I wasn't allowed to see the first Die Hard because of the bad language, " he says. "Catholicism is a great instiller of guilt. The Jesuits definitely had a hand in bringing me down to earth.

They still do. My school was very into sport. The acting programme was almost nonexistent. All the actors in the school were considered geeks and outsiders. The guys who played semi-pro lacrosse are the really cool alumni. I'm just the guy who did that Apple commercial."

Being Bruce Willis's new buddy is likely to change all that. "It was a surprise to me how funny he was, " he says. "He's stayed true to who he is. He could easily have walked through this movie. He's done three others. Yet he was on top of everything. I assumed on a big movie like this they'd have every line fixed. They have to plan the stunts so meticulously.

"The director of photography has to have everything mapped out. But to my surprise the dialogue and what happens between the characters would change on the day we shot it.

They'd throw lines out and we'd improvise. Bruce was like, let's try this. It suited me because my background is in improvisation.

Things I came up with stayed in the movie, just like when I'm doing low-budget stuff."

Bruce Willis got where he is by responding to the moment. "I'm so much a believer in everything happens the way it's supposed to happen, " he says. "I'm sure you know from your own life how sometimes the worst thing that happened to you led to the best thing that ever happened to you. I got to do the first Die Hard because Cybill Shepherd got pregnant. So I got released for 11 weeks from the Moonlighting TV series we were doing and I went off and shot Die Hard."

While he was doing Die Hard he met and married Demi Moore, with whom he had three daughters before they divorced in 2000.

She's now married to Ashton Kutcher but they all go on holidays together. So what if Cybill Shepherd hadn't got pregnant?

"I hate the 'what if ' game, " he says.

"It's what you guys do. It's your job.

Fortunately I don't have to do that. I look at it from the positive side that all these things were meant to happen. I might not have met with Fox to do a fourth Die Hard if my 15-year-old, Scout, the week before hadn't said, 'You know you should watch that movie Underworld.' So when Fox called and said I should meet with Len Wiseman who directed Underworld, I said okay. And here we are."

Up to then Die Hard had been in limbo. "After 9/11 a lot of action movies that dealt with terrorism were put on the shelf, " he says.

"Die Hard was one of them. It was our task not to dishonour the memory of people who lost their lives. So we turned it around, having the US attacked from within by someone who knew the system so well they were able to take it down."

Die Hardmakes the plausibility of this threat disturbingly convincing. "When you really deconstruct it, it's scary that the possibility exists, " says Long. "I've become so totally dependent on my cellular phone it's like another appendage. All my memory, all my music, all my work is in computers.

That's how our world now functions. We're all so connected by this breakable computercontrolled infrastructure."

So what if that really happened, Bruce?

"Hey, " he says. "I'm John McClane. You've seen what happens."

'Die Hard 4.0' opens nationwide on Wednesday 4 July