So, the car's the star...
"The flying car's great. It really works. I watched this afternoon from out front and at the end of the first act when it flies, it's quite spectacular."

What was your first banger?
"My first car? A 1947 Hillman, airforce blue with running boards. The gearbox was a bit sloppy but it was very good on cold mornings when the oil was thick. It was a bit clapped out, but it was my car. I was pleased with it."

Was it a problem getting the film out of your head when you started rehearsing?
"I wouldn't have wanted to get the film out of my head. I thought Robert Helpmann who played The Child Catcher really brought something to the character. Everybody shuddered at him and enjoyed shuddering at him. It was a definitive 'evil person'. The audience has certain expectations and if I came on looking completely different they wouldn't be happy. When I'm first revealed, I can feel the audience's pleasure that The Child Catcher has arrived."

Any Dick Van Dyke impressions in the show?
"What? [bad cockney accent] 'Maiweee Poppeeens!' Oh no! I have to take my hat off to Michael Ball."

Talking of Michael, I did a quick internet search and found 446,000 sites for you and 1,160,000 referencing Michael. It seems he's the bigger cult.
"Michael is a big, big star, but I think you'll find - and I'm not trying to detract anything here - most of his fans are in the UK. My fanbase may well be smaller but it's probably more international. I wouldn't go too much on what you get from the internet. I was in Romania recently making a movie and the film people came to me one day, saying 'Oh, Mr O'Brien we had no idea you're such a big star!' They showed me an internet download of my work and I didn't recognise any of it. Film after film came up and I'd never heard of them."

Never done a spot of ego-surfing?
"I don't go anywhere near technology. Whoever pinched the name Richard O'Brien' for the web and registered it was probably hoping I'd come knocking on their door to pay them for it. Well, f**k them! They can keep it."

Will Rocky Horror fans enjoy Chitty?
"I think Rocky Horror is an enjoyable, musical, rock 'n' roll fairytale and I think Chitty Chitty Bang Bang fulfills all the requirements of panto-fairytale land."

The RSC's Adrian Noble is directing. Was he hard to work with?
"I don't think I've worked with a less demanding director. He seems to get everything done with the minimum need for taking power, posturing or bullying. I don't know how he keeps his temper. He told me that he rarely sleeps. I get very ratty when I'm tired but he's a sweetie."

It's a real star-studded show. How is newcomer Emma Williams coping?
"Emma's fine. She reminds me of Jane Horrocks, simply because Emma's from Halifax and she talks like Jane. Of course, when she's on stage doing Truly Scrumptious her vowels are all rounded and wonderful. [sings an impression] 'Way across the bay, you are delicious!' It's so Julie Andrews. All that enunciation!"

Is the scene where she pretends to be a wind-up doll in the stage show?
"Oh, yes. [sings another impression] 'What do you see?'"

That's it! That's my abiding memory of the film. What's yours?
"The Child Catcher. The film becomes quite German expressionistic at that stage. That's one of the reasons I wanted to play the part. I hope I bring a little bit of that warped 1930s Grand Guignol to proceedings."

When you heard about the Child Catcher role did you immediately want it?
"When I saw Adrian Noble, I told him he shouldn't see anyone else after me. I thought it would be perverse to do so. I know that sounds arrogant and rude but sometimes I have to wear a producer's hat. If I was the producer, I would think Richard O'Brien is the right person for this role. Fortunately, I got the gig."

You have old violins all round your dressing room. Do you play?
"I don't. I buy old broken instruments. I went along to a sale the other day and I came straight here afterwards so I brought those back with me. They're just a lovely shape and beautiful instruments. I hang them on the wall. I've got a lavatory full of musical instruments at home - cellos, harps and guitars."

You've got a long run ahead. How will you keep yourself interested?
"I find that doing a long run is wonderful. It's like drawing a rough sketch and turning it into brilliance, getting rid of the mistakes and the rough edges. It takes an awful lot to bore me. I think small minds get bored. You can always make something better by simplifying and getting rid of the egos."

Do you need to get rid of the ego?
"I have lot of ego, narcissism and exhibitionist qualities, but I ever take that on stage. In my entire life, I've only ever had two moments on stage that have been pure epiphany. Both times I knew I was as pure as one could ever be.

"The first time, I was asked to sing a couplet in Hair that someone else usually sang. It came out of my mouth so gently that I didn't think it would go over the footlights, yet I knew I was filling the entire theatre. Helen Chapelle, the finest singer in the company, said it was the purest voice she'd ever heard. The next night I tried to recreate that moment but it just didn't happen. It didn't happen again for another 30 years.

"I was in Milan, they were doing Rocky and asked me to do the reprise to 'Science Fiction'. I went to sing and realised I couldn't hear the band. I very hesitantly sang the first line with some musical notation I'd never even conceived could be sung! There was a pause then this roar from the audience. I walked off, as I had 30 years ago, thinking 'where the f**k did that come from?'"

What's next after Chitty?
"I'm very naughty and lazy because I'm supposed to be writing a sequel for Rocky. Once we're up and running I have to go back to that and finish it off. We'll then workshop it at the end of the year. That's the plan."

Will you be in it?
"No no no!"

I hope you have an epiphany tonight.
"That would be nice. I don't think you can make them happen though, they happen to you. Like special moments in your life, happiness can't be engineered. It happens unexpectedly. That's the pleasure, that's the epiphany, the magic moment. Cresting a hill and seeing a beach and a blue sea you weren't expecting. Breathtaking!"