It’s a much overworked phrase, but Mickey Rooney really is a Hollywood legend. His cherubic face has appeared in over 200 films, and he’s worked with the likes of Lana Turner and Judy Garland. He’s been married eight times, most famously to fellow Hollywood star Ava Gardner in 1942. “They soon divorced,” Mickey’s website cryptically remarks.

Joe Yule Jr, as Mickey was originally named, was born on September 23, 1920. His parents were vaudeville performers — vaudeville being the American version of music hall.

Legend has it that at the age of 17 months, young Joe was hiding in a Chicago theatre, watching his father’s act, when he sneezed. A spotlight swung on to him. Not knowing what to do, he stood up and blew on a tiny mouth organ, hanging on a string round his neck.

The audience erupted with laughter, so the show’s manager took the hint, and bought him a pint-sized tuxedo. He began to perform small ballads and speeches. Mickey Rooney’s career had been launched.

But, Mickey’s mother decided, the future lay in films. So they headed off to Hollywood, and on a second visit Mickey landed his first film role in Not to be Trusted. He played a midget.

His career, however, became anything but midget-sized: according to Halliwell’s Film Guide: “By the late 30s and early 40s he was the most popular film star in the world.”

That’s quite some accolade, when you think of the competition he was up against. August film critic James Agee once described him as: “A rope-haired, kazoo-voiced kid with a comic strip face.”

It was a surreal experience to walk through Milton Keynes shopping centre (itself now up for listing by English Heritage as a Grade II* structure of historic significance — Mickey Rooney was already 59 when it opened), and on into the adjoining theatre, there to see the man himself, sitting in a glass-walled office, rather like a goldfish in a bowl.

Why swap his Hollywood home for Milton Keynes in winter? Two years ago, Mickey made his debut in British panto, playing Baron Hardup in Cinderella at the Sunderland Empire, and this Christmas he reprises the role at Milton Keynes Theatre.

“I’d never heard of panto before,” Mickey told me when I was ushered into his presence. “But being always interested in newness, and finding out what’s going on, I’ve enjoyed doing it ever since. I think panto is a good way of sharing — laughter, children. People enjoying themselves, and enjoying what you’re doing. It’s payment enough.”

Talking of payment, Baron Hardup is by tradition an underdog, the family silver long since sold to pay off debts — not to mention the wardrobe bills of his step-daughters, the Ugly Sisters. “In the early 1970s,” his website reveals, “Mickey undertook several short-lived financial ventures.”

So how much of Mickey Rooney is there in his portrayal of Baron Hardup?

“Everything. Every time. You’re not going to please everybody, but you do your level best. I don’t build anything into characters, I do what I have to do at the time that I’m doing it.

“We’ve all done things we didn’t mean to do. That applies to everyone. But you should do what you can at the time, you should do your best — not next to your best, but your best.”

By now it has become apparent that, unlike most 89-year-olds, Mickey is not in the least interested in looking back. Marriages, fascinating pieces of theatrical and cinema history, life in Hollywood decades ago — all are a firmly closed book.

“That’s all gone, it’s over with. You have to accept what is now. There is no other way. Now is the most important time. You don’t have to think about what happened 300 years ago. That’ll always be history. We only get to know by not having been here before — does that make sense?”

Even the award of an Honorary Oscar for Lifetime Achievement in 1983 is briskly dismissed.

“It’s fun having awards and things to show. But I think life is more than just awards. Celebrity? That means nothing.”

But as Mickey Rooney enters a new panto season, which would be gruelling enough for someone half his age, he is sharply aware about what keeps him young.

“Believing. Faith. God. Friends who really care: people who tell you when you’re wrong, they’re your real friends. If you go too fast, you’ll burn up. Take life for what it is, precious moments.”

Cinderella opens at Milton Keynes Theatre tomorrow, and runs until January 17. Tickets 0844 871 7652 or online at the wesbite ambassadortickets.com/ miltonkeynes