At the age of 70, and with a career spanning six decades, Billy Connolly can hardly be described as a young pup. But on the set of Dustin Hoffman’s directorial debut Quartet, the Scottish comic was, as he declares proudly, “the baby of it all”.

Romford Recorder: Behind the scenes of Quartet. Pictured: (l-r)Maggie Smith, Dustin Hoffman and Tom Courtenay. Pic: PA Photo/Momentum Pictures.Behind the scenes of Quartet. Pictured: (l-r)Maggie Smith, Dustin Hoffman and Tom Courtenay. Pic: PA Photo/Momentum Pictures. (Image: Archant)

Connolly plays Wilf, a former opera singer with an eye for the ladies, in the gentle comedy about a retirement home for classical musicians.

When casting, Hoffman was concerned that the sprightly star - who holds his own among veterans such as Dame Maggie Smith and Sir Tom Courtenay - would look too youthful.

“As you notice I’m not very wrinkly and I have this going on,” Connolly explains, motioning to his long, white hair and goatee beard. “But they thought they could make me look older and they did. They cut my hair and aged me up a little.”

The New York-based star cuts a dash in trendy thick-rimmed glasses, patchwork trousers and a sharply-cut jacket when we meet.

Always one for memorable outfits - from monochrome striped suits to banana-shaped boots - the notion of growing old gracefully is one he rails against.

“I think disgraceful is the way to do it. Be a nuisance, stay alive,” he says. “In this bit of the world especially, not so much in America, but in Britain you’re encouraged to wear a cardi and have the crotch of your trousers away down at your knees - bum fainters they call it in Scotland, because if you look at it from behind it looks as if your bum’s fainted.

“You’re constantly told to grow up. ‘Grow up, it’s time you grew up, you’ve got some growing up to do boy’. What they really mean is, get boring, stop being angry, stop being interesting, stop being a nuisance.

“I would say don’t grow up. By all means grow old, but don’t grow up. Don’t be beige.”

The funny man, known to his fans as The Big Yin, has come a long way since his early days as a Glasgow shipyard welder. After achieving global success in stand-up comedy, his breakthrough film role came in 1997 alongside Dame Judi Dench in the drama Mrs Brown, in which he played Queen Victoria’s favourite servant John Brown.

The performance earned Connolly a Bafta nomination, and parts in Hollywood blockbusters followed. But the star was still unsure about signing up for Quartet, in which he, Smith, Courtenay and Pauline Collins play former singing partners.

“Before I did it I thought, ‘Oh my God, I can’t act with them, they’ll be acting all over me and I’ll be standing like a fool not knowing what to do’, but it wasn’t like that,” he recalls.

“I should’ve remembered that from my experience with Judi, it was so good. And as a comedian, working with other comedians, when you work with good ones, or musicians, it makes you good.”

Connolly says Hoffman encouraged the actors to improvise.

“Dustin gave us loads and loads of freedom. Not only that, we would do these 12, 14-hour days, like you do when you’re filming, and then he would go off and work at night on the script.

“Then he’d come back in the morning looking a little tired but behaving like 100 per cent, having changed a lot of things. It kept the whole thing alive and well.”

In another effort to make the movie - based on a play by Ronald Harwood - feel authentic, Hoffman cast retired opera singers and musicians for the supporting roles.

“That was one of the best parts of the film,” says Connolly, himself an avid folk musician. “They were real musicians and they played all the time like real musicians do. You can’t stop them, between takes you felt them playing. And they hadn’t had a phone call in 20 years, most of them. They were all lead players, ace players, but they hadn’t been asked to work because of their age, which is really weird.”

He adds: “It’s a very modern thing, that dependence on youth. If you get old black and white movies, those movies in the Forties, movies were all full of old people. There were hardly any young people. The young people were played by people in their 30s or 40s. The young crumpet would be 35 or 38, mincing around.

“There was a change in the Fifties. I think they invented the teenager in the Fifties, there was no such thing before that, and they stuck them in everywhere they could.

“I hope they just get back to the way they did before, or a mixture of the both, and use older actors instead of having the token old one, like Driving Miss Daisy, every now and again. Have it the way life is, a mixture.”

Quartet is in cinemas now.