Fans of the Apprentice TV series might remember a particularly cringe-worthy attempt to win a task which resulted in the creation of an unlikely superhero known as Pantsman.

Simon Pegg would be a shoo-in for any future screen adaptations as the wearer of the mighty tighty wighties.

He got plenty of practise while making A Fantastic Fear of Everything, playing an author who has apparently lost his trousers along with his grip on reality.

Simon was persuaded to don the crusty looking Y-fronts as a favour to his friend Crispian Mills, better known as the singer/guitarist from Kula Shaker, who was making his directing debut.

“They were not method pants,” stresses Simon. “They were never quite as grotty as they looked. Lou Foley, our brilliant costume designer, who rather spectacularly distressed those pants, had them fresh clean for me every morning.”

He says he found it quite liberating to wander about on set half naked.

“It’s nice to go to work in your pants.

“I would often fall asleep between takes in my special chair in my pants, and my cashmere jumper. I couldn’t tell you how wonderful that was.”

The 42-year-old star looks considerably more groomed during our chat at a London hotel. Dressed in a pale blue shirt and jeans, his strawberry blonde hair is cut short and swept back off his face and his goatee is neatly trimmed.

As Jack in Fear, his unbalanced mental state (a result of over-immersion in research for a book about Victorian serial killers) has resulted in a collapse of his personal hygiene regime, his long curly hair flying wildly about his head.

“I looked like a tramp,” says Simon. “I’m not a method actor but it was fun to immerse myself in this character and become a bit of an animal.

“The hair was a wig. When my daughter came to see me at work she’d be quite freaked out because she couldn’t work out how my hair had grown so long so quickly.”

Simon, who was born in Gloucester and first studied acting at college in Stratford-Upon-Avon, concedes it was probably due to his involvement that this small budget comedy/horror finally became a credible contender for a big screen release.

“We (together with Nick Frost and Edgar Wright) have had a number of successes in this country so my domestic ability to get films made at the moment is healthy.

“It was nice to read the script and to think I could champion it.

“Shaun of the Dead and Hot Fuzz are probably more accessible than this one, indebted to more mainstream ideas.

“This film is a little more avant garde, a little weirder and more willfully obscure.”

Simon knew Crispian through his wife, who had worked with him and his record company.

“He brought me the script and I thought he just wanted some advice or something.

“When I realised he wanted to direct it. I was like ‘but you’re a guitarist’.

“As soon as we got on set I realised, of course, it was in his blood. His decision to become a musician was probably some weird rebellion against his inevitable joining of his dynasty.”

Crispian’s heritage was brought home when his mum Hayley, daughter of Sir John Mills and a huge child star herself, visited them on set at Shepperton.

“It struck her suddenly that this was where she had met Roy Boulting (the director and Crispian’s father). It was the same sound stage they’d made The Family Way in.

“We were making a film in the room responsible for Crispian’s existence. It was like ‘You’re part of the DNA of British film!’.

“And Amara Karan (who plays Sangeet in Fear) had just done the remake of The Family Way and spoke to Hayley about it

“I’m the least spiritual person you will ever meet but there was so much weird confluence on this film I started to believe all Crispian’s moon mumbo.”

Simon’s cinematic success hasn’t been limited to the domestic market. The cult popularity of rom/zom/com Shaun and Hot Fuzz, which successfully aped blockbuster action movies in a twee English village setting, acted as a platform for parts in Mission Impossible and Star Trek.

For all his pragmatism. Simon can still get star struck,

“Paramount is 100 years old this year and we had a group photo of 100 people that have been involved with the company over 100 years.

“I was invited to be part of it and I have never been in a room where there were so many living legends.

“Kirk Douglas, Shirley MacLaine, Jack Nicholson, Steven Spielberg, Harrison Ford, Martin Scorsese, Robert De Niro, Mickey Rooney, Jerry Lewis...

‘‘It was like being in a waxwork museum come to life.

“I had a conversation with Meryl Streep about Margaret Thatcher. She is such a lovely lady, and I said ‘How dare you make Margaret Thatcher so nice’.

“I sat with them all having my picture taken and thought ‘I am from f****** Gloucester, what the hell is this all about?’.”