WHO hasn't heard of the Chinese martial art Kung Fu or that great British tradition, the pub crawl?

But Pub Fu? That's a new one.

However, this amalgamation of pastimes is artfully demonstrated in The World's End, starring Simon Pegg and Nick Frost.

"It was fantastic – I got to fight 10 men at once and didn't get hit," says bearded Frost, 41, recalling the scenes in which he and co-stars Pegg, Martin Freeman, Paddy Considine and Eddie Marsan release their inner action men when a routine pub crawl takes an unexpected turn.

On hand to assist was stunt co-ordinator Brad Allan, who has worked with martial arts legend Jackie Chan for years.

"He's serious, but sometimes you'd see him laughing at the monitors at something you'd done and you'd feel amazing," says Essex-born Frost.

The British sci-fi comedy is the third film in Pegg and Frost's Blood And Ice Cream trilogy following 2004's zombie romcom Shaun Of The Dead and 2007's cop comedy Hot Fuzz.

The latest story begins in 1990 in the town of Newton Haven when five teenage boys celebrate leaving school by attempting – and failing – an epic pub crawl.

Twenty years later, the 'five musketeers' have grown up and moved on, with the exception of irrepressible ringleader Gary King (Pegg), who is hell-bent on reuniting the gang and tackling the 12-pint 'Golden Mile' again.

Unenthused, the others go along with Gary's plan but soon realise something odd's going on in their home town, and the pub crawl begins to unravel.

"It's a bigger proposition for us than the earlier pictures," says Pegg, 43, sitting next to his long-time friend Frost. As with the two earlier films, Pegg co-wrote the script with Edgar Wright (who has directed all three) and reveals that the pub crawl element "partly came from a script Edgar had toyed with at a young age", based on one he and his friends attempted as teens.

They didn't make it past pub six, but that sense of it being a quest stuck with Wright. This time, though, the drinking marathon is just the beginning.

"When you go back to your home town, you experience this simultaneous feeling of familiarity and alienation. You can't put your finger on what it is.

"It looks the same but it isn't – and that's because you are different, it's not different," says Pegg, who is from Gloucester, but now lives in London with his wife Maureen and daughter Matilda.

"We thought it would be funny if [in the film] the reason it feels different is if it had been taken over by alien robots."

The pair couldn't have had a better time on set. "We just hung out," says Frost. "I wish I could tell you some story where we all hated one another but we just laughed a lot.

"It was that thing where you get home and you have your shower and you get your bag ready for the next day and you think, 'I can't wait to get in', and that's a rare thing in any job."

It wasn't all laughs though. "We all had a moment in the film where we're angry or upset or sad and it's serious acting, not just goofing around," says Frost. "But it all felt very supportive."

At least they all knew each other. Freeman and Considine starred in the trilogy's earlier titles, while Marsan was one of the dwarves in last year's Snow White And The Huntsman alongside Frost, and was directed by Considine in the bleak drama Tyrannosaur.

LEFT alone, Paddy will just dance around and say things inappropriately," reveals Frost.

"Martin's a dark horse," adds Pegg. "He likes to make you laugh but pretends he's not doing it."

And Marsan? Well, Pegg was keen to show him in a softer light on screen. "Eddie's a master at playing bad guys," says Pegg. "I mean he refers to himself as 'Rent-a-villain-Eddie-Marsan' and we loved the idea of him playing a sympathetic, loveable character."

Among all this testosterone, former Bond girl Rosamund Pike, plays Freeman's sister.

"She gives as good as she gets, and throws herself into it," says Pegg. Frost adds: "But we were protective of her. When it was cold, the five of us would crowd around her and give her a penguin cuddle."

Banter aside, there was a reason Pegg "relished" the movie. He went through a Goth phase in his youth ("There was a lot hairspray, tight trousers and winkle pickers"), so leapt at the chance to dress Gary as a Goth. This time round, he even dyed his gingery-blonde locks black.

"I never dyed my hair when I was young. I always thought it would upset my mum, so to do it felt like I was putting something to bed," he says, laughing.

Frost, who lives in London with his wife Christina and their son, was a raver, back in the day.

"And still am," he adds. "Well, my fashion's different but I still listen to that music now."

l The World's End is released in cinemas on Friday

Actors Simon Pegg and Nick Frost hope to follow the huge success of Shaun Of The Dead and Hot Fuzz with a pub-based sci-fi comedy. The best mates tell Susan Griffin how the idea for the movie became a reality