Musicals are my children

Essentially, he has fallen foul of the Musicians' Union because, during the move, Mackintosh is cutting the orchestra for Les Mis down from 22 to 11.

Even worse, he is replacing the lost members with a whizzy new computerised American music system called Sinfonia. "The musicians are worried that they are about to be made redundant," says Mackintosh, "but that's never going to happen."

Anyway, the problem seems to be that Mackintosh has been accused of discarding musicians in a cynical attempt to cut costs. "No, that's not it at all," says Mackintosh. "Firstly, look at the orchestra pit." I do.

It hardly looks big enough to swing a cat. "Can you see 22 people fitting in there? Secondly, running a theatre, putting on shows, that's not done for charity. This is a smaller theatre. We will have smaller numbers attending.

We cannot lose any members of the cast because they are all doing about four roles each as it is. Everyone thinks I just sit here and make money, but that's not necessarily so. Every show you put on is a risk."

Luckily, many shows of his - Cats, Phantom of the Opera, Miss Saigon, My Fair Lady - make a lot of money. His next project, which premieres in Bristol, is Mary Poppins. "It's going to be marvellous, I pray, I hope," he says. "We're going to get it all right and sparkly in Bristol and then bring it up to London."

But didn't he say, five years ago, that he wasn't going to put on any new musicals in London? "I did, I did!" he says. "But, you see, I've been working on Poppins for years so I felt it didn't really come under that umbrella.

What I meant was that I don't feel it's my job any more to find new talent and nurture new things. Look at me. I'm 58 now. What do I know about what's in, what's new?"

But he looks so young. Exuberance flows out of his pores. "Yes, I know that," he says. "I love the theatre. But all these musicals, they are like my children. I have nurtured them and looked after them but, however much energy I have or Andrew has, I don't think like a 30-year-old."

There is a small problem, though. It seems to be that no one has come along to fill his and Lloyd Webber's shoes. "When Andrew and I met," he says, "maybe it was time for that golden age of musicals to be revived."

It turns out they first bumped into each other at the Olivier awards when they were hosted, often by Mackintosh himself, at the Café de Paris.

"Anyway, one year Andrew was winning an award for Evita and I wanted his cast to do Don't Cry For Me Argentina because it only needed one microphone and our budget was tight. Andrew wanted - typically - to put on some razzle-dazzle number that needed six mikes and the works. Of course, he got his way, and it was a fiasco and I was so cross."

Two days later, he received an apologetic note from Lloyd Webber and the two arranged to meet. "Oh, how can I explain what it was like?" says Mackintosh. "We clicked. I'll never forget that lunch. It was like Romeo and Juliet, but I've never worked out which of us is which."

He admits that, over the years, they've had their ups and downs. "Of course we have," he says. "Who wouldn't have done over that period of time? I probably like to control things in many ways because I have such a vision in my head.

Andrew may not want someone to do that all the time, especially not the producer, but that's all it's about. We're very close again now. We're seriously working on bringing back Evita to the stage so we've obviously not fallen out too badly!"

But why Evita, another old musical, and why now? "Oh, musicals change their meaning," he says. "Camelot didn't mean what it means now until JFK was assassinated. I think Evita has a resonance for a contemporary audience, especially after the death of Diana.

It's not about Argentina, it's a fairy story. That's what people have to understand about musicals. Les Mis appeals to the audience on many levels and none of them are to do with being French."

When it first occurred to him to bring back My Fair Lady to the stage he realised pretty quickly that he needed a star with which to launch it. He already had Jonathan Pryce, who had worked with him on Miss Saigon.

"When I saw Martine McCutcheon and heard her sing, I realised she was perfect." But it all went a bit wrong, with McCutcheon forced off stage with a virulent throat infection. "It was disappointing," he says. "But you have to remember that she hadn't done anything like it before. It's very demanding."

He was rumoured, at the time, to be rather cross with her. "I don't think I was," he says. "In fact, it gave others a chance to be Eliza. Alex Jay, her understudy, was marvellous and then we had Laura Michelle Kelly and she was fantastic and now she's going to star in Mary Poppins!" Would he employ McCutcheon again? "I don't have any roles available right now," he says diplomatically.

So, if Cameron Mackintosh can make so many productions work for him here and across the world, why can't others? Maybe it's to do with his childlike fascination with the genre.

"I've always loved them," he says, "ever since my aunt took me to see Salad Days when I was 10." From there he progressed to putting on shows at the family home in Cuffley, Herts. "They consisted of my two brothers and myself doing puppet shows."

He also started producing small shows at his boarding school, Prior Park in Bath, and selling tickets in the playground. " I was very entrepreneurial," he says. He claims he gets that from his mother, Diana, who was half-French, half-Maltese.

"She knew how to survive," he says. "She'd make a chicken for two go round six." His father, Ian, he says, was a different kettle of fish. "He used to play in a jazz band," says Mackintosh, "but he took his responsibilities very seriously and ended up running a timber yard. He still played but not professionally, which is probably what he would have liked to do."

It was his father who insisted Mackintosh did not just abandon his education. "After my A-levels I was determined to go to work," he says, "but my father wanted me to go to university. I said I'd only go if I could study drama."

In the end, he went to the Central School of Speech and Drama in London but left after a year. "It was a waste of time," he says. "I wasn't going to be an actor. I wasn't going to direct. I wanted to produce and that's all I've ever wanted to do."

Now, here he is, all those years on, having done just that. And he's made a fortune from it. He is, reputedly, worth £400 million. He has homes all over the place: London, New York, Provence, Scotland, and a farm in Somerset where he lives with his boyfriend of two decades, the rather wonderfully named Australian photographer Michael Le Poer Trench.

Mackintosh never really talks about his sexuality. "Oh, it's always been common knowledge," he says. "It's a very small world, the theatre world. There's a half-dozen of us who circle round each other and then all the other people we employ - stage technicians and lighting people and sound people.

We all know each other very well, so my sexuality has never been an issue." He inadvertently outed himself when he put a signature to a letter supporting Ian McKellen's knighthood. "It was from all the gay people in the business," he says, "so obviously people drew their own conclusions."

He also, of course, has his seven theatres. "Listen," he says, "I love my theatres. I love my homes but, honestly, you can have too many!" He is in the process of refurbishing most of the theatres to the tune of £35 million "and counting", he says. This is his way of redefining the West End theatrical experience.

"I can't clean up the West End," he says, "but what I can do is make a commitment to my own theatres and hope others will follow my example." He is totally re-doing the Prince of Wales theatre, which will open in eight weeks' time with Mamma Mia!

He marches me down the road to take a peek. All is dust and workmen but Mackintosh is so excited by his new soon-to-open theatre that it's impossible not to get excited too. Then we march back to the Queens which, he says, at some point he will tear down and rebuild lock, stock and then add an entirely new theatre, The Sondheim, on top.

"I am going to make theatres accessible and comfortable," he says. "I am going to add huge, airy foyers and bars and many more ladies' loos. People are always complaining that tickets to a West End show are expensive but, look at it realistically. Fifty pounds is the top price. Most people would spend that on an evening's dinner, with wine, and not even think about it.

"I am going to give theatregoers a most spectacular experience. They will go home having had a marvellous night out that they will remember a lot longer than a meal."

With that, he squeezes me on the arm and rushes off to see John the lighting man. "It's like having a big toy box with everything you've ever wanted," he says, calling behind him. My theory, for what it's worth, is that he's not going to give up playing with this one for quite some time yet.