Sir Michael Caine's elixir of Youth

It is not often that an 82-year-old actor is offered the leading role in a movie, even when you are Sir Michael Caine. That's the opinion of the Oscar and Bafta-winning star himself, adding that it's even more unusual when the film in question is called Youth.

For his first leading role since 2009's Harry Brown, Sir Michael stars alongside Harvey Keitel, Rachel Weisz and Jane Fonda in Youth, the second English-language movie from Italian director Paolo Sorrentino.

In 2014, Sorrentino's film The Great Beauty won the best foreign language film Oscar, and Sir Michael says he was surprised to get a call from his agent a short time afterwards.

"She told me: 'Paolo Sorrentino's called and he's written a film for you'. I was completely staggered.

"It's not like we mix in the same film circles and I wondered how on earth he had ever heard of me. She said: 'If you don't do it he says the movie won't get made at all'. Fortunately I read the script and I thought it was just fantastic."

The part the director had written for Sir Michael is of a former conductor, Fred, who has now retired. He is on holiday in a spa resort in the Alps with his friend Mick, played by Harvey Keitel, and his daughter, played by Rachel Weisz.

Jane Fonda and Paloma Faith also make cameo appearances. While Mick struggles to finish what he believes will be his last screenplay, Fred turns down an offer to come out of retirement - but even he is forced to think of what his legacy will be.

With credits for nearly 120 movies during his career, Sir Michael says his attitude to life is the opposite of his character's, who retorts when urged to do some exercise at the spa "at my age getting in shape is a waste of time".

By contrast, the actor says: "I've never had it so good, and this time of life is fabulous for my career. Now I try to test myself when I accept a role on whether it will take me farther and farther away from who I started out life as.

"A classical music composer is as far away as you can get from a Cockney tearaway, who was the son of a charlady and a fish market porter."

Born in London in 1933, Sir Michael served in the army and did a series of odd jobs until his first big movie role came with 1964's Zulu, directed by Cy Endfield - although his first Oscar nomination didn't come until 1966's Alfie.

He has since been nominated five times, and won twice. The actor says he doesn't "take anything for granted these days".

"A friend of mine says that at least when you wake up and you feel your aches and pains, you know you're still alive. But what I love about this movie - it has a great view of old age. It tells us that if you are going to get there, it's really not so bad."

Asked which of his own films he's enjoyed most, Sir Michael names Zulu, Educating Rita, Alfie and the Cider House Rules. But he adds: "I've been in a lot of movies, and it's hard to say which ones I've preferred."

But he says he finally feels "on top of his game".

"I went to the top and then I went down to the bottom," he says. "Every actor probably does. I screwed up and took a couple of scripts that weren't that great. I tell you what the transition was for me, it was when I was around 60 and I read a script and sent it back to my agent, saying 'the part is too small'. She said, 'they're not asking you to play the lover, they wanted you for the father'.

"I thought, 'that's it - I don't get the girl anymore'. So overnight I changed from being a movie star, where you get the girl, to being a movie actor, where you get the parts and the characters. And then I won a couple of Academy Awards and a Bafta so it wasn't so bad."

The Oscars and Bafta were for his roles in Educating Rita, Hannah and her Sisters and the Cider House Rules, but Sir Michael says the part in Youth, which won three European Film Awards last year, has stayed with him, "because I absolutely disappear in this film".

"That's the real test for me in a role - can I still see me when I watch it on screen? And in this case I couldn't, not at all."

While acknowledging his "extreme good fortune" in reaching old age at all, Sir Michael asks his fans to remember "that it's only your body that gets old. Inside my head I am still 38".

"Why 38? Well I married my wife [Sir Michael married Shakira Baksh in 1973] and it was wonderful - we were in love, I married the most beautiful woman in the world, I was fit, healthy, happy, rich, famous, you name it. I didn't realise that there was one more incredible gift to come, and that was grandchildren."

The actor will next be seen in Going in Style with Morgan Freeman, directed by Garden State's Zach Braff, about three retirees who plan a bank heist. Sir Michael says "every decade of life has been happier than the last one for different reasons, and I think that's what happens in Youth - everyone ends up happier.

"I don't have any regrets at all. I tell my daughters that all the time - 'don't look back. You'll only trip over'."

Youth is released in the UK on 29 January.