NOT a lot of people know this, but when Sir Michael Caine acts angry he curls his lips.

Among the few privy to this knowledge are the Pixar animators, the creators of Toy Story, who had the job of turning him into a 1966 Aston Martin for Cars 2. Is that any way to treat a double Oscar-winning knight of the realm? Caine thinks so.

“I sat there in absolute astonishment,” he says of the finished Pixar product after voicing the character of Finn McMissile, a British secret service chief. “I’m so glad I did it.”

He agreed to do the movie for a number of reasons. “In quite old age I suddenly had three grandchildren and I thought, ‘They’re never going to see me in any movies for years’,” he says. Among his most recent films was the vigilante drama Harry Brown, certificate 18.

There were other reasons for signing up for John Lasseter’s film. Actors are a superstitious lot, he says, and Cars 2 had several good omens. The character was a spy, like Harry Palmer. It was about cars. See The Italian Job. The moniker was promising, too. “Finn McMissile. That’s a great name. You know there’s going to be trouble. Someone’s going to get hit.”

Pixar had their star voice and it was time to turn the actor, born Maurice Micklewhite in London in 1933, into a car. Supervising animator Shawn Krause says: “There are two things we focus on when we are trying to get to the soul of these cars: the eyes and the mouth.” Hence the curl of those lips.

Krause’s team are not the first to try to pin down Caine’s essence. Leaving aside such duffers as Jaws: The Revenge and Blame it on Rio, among his more than 100 films are movies which can lay claim to classic status: Zulu, The Ipcress File, Sleuth, Alfie, Get Carter, The Man Who Would Be King, Hannah and Her Sisters, The Cider House Rules, Educating Rita, The Quiet American. Yet this is one national treasure who defies easy categorisation and who for a long time went unappreciated. Like the BBC and a civilised attitude towards queuing, he has always just been “there”.

At 78, he’s not going anywhere either. “I’ve been asked if I’d retire,” he says, the eyes behind the specs crinkling with amusement. “If you’re in the movies you don’t retire – the movies retire you. If you have no luck, probably on your first movie. The great thing about being an actor is you don’t ever have to retire because someone’s got a movie with a 90-year-old bloke in it and you’ll get a job.”

He puts his career longevity down to how he first started out after leaving the army in 1953. “My mentality is still that of a repertory actor. And a critic. I’m my own worst critic. I keep looking for new parts that will force me further and further to be better and better.”

Although Cars 2 ticked lots of boxes for Caine, he’s hardly Jeremy Clarkson when it comes to motors. As a working-class lad, he didn’t know anyone who owned a car until he was 25.

Then, with money coming in from films and television, he decided to get his own wheels. Not just any starter car, though: he bought a Rolls-Royce. “The premium was so high it was cheaper to hire a chauffeur.”

Moving to Los Angeles, he had to get a licence to get around. Before he went for the test, he was given a long list of do’s and don’ts, chief among which was not to chat with the examiner.

“I got in the car and the guy looked at me and said: ‘I loved you in The Man Who Would Be King. You’re going to have to be **** to not pass this test’.” At 50, he finally got his licence.

He gave up driving when he was 70, and admits to never being that good at it: “My mind is always somewhere else.” This from the star of The Italian Job? Therein lies another anecdote that would have had Parky audiences chuckling into their Saturday night G&Ts (it was on Parkinson that Caine revealed it was Peter Sellers, impersonating Caine, who invented the catchphrase: “Not a lot of people know that.”).

“I drove the cars in a controlled area but even there I didn’t do the dangerous bits. A stunt driver’s wife doubled for me because she had short blonde hair. She was a better driver than any of the guys, so I came out of it looking very good. A little feminine but a very good driver.”

Caine has acquired a new cool recently as Alfred the butler in Christopher Nolan’s Batman series. He’s also cool with the Coen brothers, who have written the script for a remake of Gambit, with Colin Firth as cat burglar Harry Dean, the role Caine played in the 1966 original. Above all, he’s cool with the grandchildren: “I spend my life watching cartoons with them because the biggest TV is in my office and they all come in there, They won’t watch cartoons anywhere else.”

His name is Sir Michael Caine, granddaddy of cool.

Cars 2 opens in cinemas tomorrow.