Mrs Henderson Presents is a cold bum movie. No, that's not some cheap dismissive comment, it's a statement of fact. Well, a statement of Bob Hoskins fact anyway.

"The way I judge a script that turns up in the morning is to give it the cold bum test," he laughs.

"I take it to the loo. And if I suddenly think 'oh, I've got a cold bum, it's obviously a good script'. Then I decide to do it." Judging by the finished film, Hoskins's nether regions must have been frozen solid.

Directed by Stephen Frears and co-starring Judi Dench, it's the mostly true story of London's Windmill Theatre and the woman behind it, Mrs Laura Henderson, who, in 1931, bought a disused Soho cinema and turned it into the most famous theatre in wartime London.

Famously proclaiming 'we never closed', thanks to Henderson the Windmill was the only London theatre to remain open throughout the Blitz. Even more famously, it was her initiative that saw it become the first theatre in England to feature nude women, posing in tasteful tableaux within musical production numbers, live on stage.

The nude shows were a huge hit with troops home from the front, looking to have their minds taken off things before returning to combat, but before, during and after the war, audiences of all kinds flocked to see the Windmill's revues. Among then a certain young Robert William Hoskins.

My mum and dad took me when I was five," he beams. "The tableaux were the most beautiful things I'd seen in my life. Before girls starting shimmying up and down poles and stuff like that, this was a real family show"People used to go there and have picnics, and there was kids running around all over the place. And they weren't just going for the nude stuff but there were comedians and all kinds of acts. It was great!"

Little did he think that, 58 years later, he'd be recreating the experience, playing Vivian Van Damm, the Windmill's theatre manager and impresario. But, not only does Hoskins co-star in the film, he's also one of the producers.

Approached by friends who'd spent some 13 years researching Mrs Henderson, Hoskins was immediately hooked and brought the project to his producing partner Norma Heyman. She rang Judi Dench's agent, lunch was arranged and Hoskins made a pitch she couldn't resist.

"Judi never reads a script," he explains, "but I leant forward and said 'Judi you get to dress up as a Chinese lady and a polar bear' and she said 'oh yes I'll definitely do it now'."

On the journey back, Heyman called up Stephen Frears and asked if he'd fancy doing a film with Hoskins and Dench about the woman who put nudes on at the Windmill. He just asked when he had to start.

Although there are obvious fictionalised elements for dramatic effect, the story remains very close to the real events, even alluding to the fact that Henderson provided the money to found the Marie Stopes clinics (she also supported the Markova-Dolin Ballet company which became the English National Ballet).

Despite the family atmosphere Mrs Henderson created within the theatre among the girls and backstage staff, there was many an occasion when she and Van Damm were at loggerheads, to the extent of him banning her from the theatre several times.

Hoskins certainly reckons the actual Mrs Henderson was nowhere near as charming as Dench's portrayal. Or, as he more succinctly puts it, "she was a right old cow".

As for Van Damm, Hoskins would seem to have been spookily ideal casting"He looked exactly like my dad," he roars.

" I was looking at old pictures of my dad and it was exactly the same haircut. My dad had a mane of hair, unfortunately I take after my mum. Well, my mum wasn't bald but her brothers were!"

And if his dad provided the look, Stephen Frears provided Hoskins with the personality model to go with it.

"When I turned up for the first day I wasn't really sure what I was going to do with Van Damm, how I was going to play this bloke," he recalls.

"Stephen said 'you've got no problem, all you've got do is play me'. That was a very good idea. Then in the middle of it he said 'no, no, no you're twinkling, I don't twinkle!'."

There's a running line in the film in which Henderson, casually anti-Semitic as were many of the upper classes of the time, keeps remarking upon Van Damm's Jewish origins.

Suppositions are settled to her satisfaction in one amusing scene where, though it may prove a little much for the faint-hearted, he seeks to make the amply curvaceous girls - the Millerettes - less self-conscious about stripping off by removing his own clothes. One wonders whether he needed much persuading?

"Well, no," he barks with laughter.

"I didn't feel too comfortable about it but everybody else was wandering around naked, so I just took 'em off. But then when I got 'em off. I suddenly thought ,'hang on, I'm the only old wrinkly here! There's all these young bodies and this old fella!"

It would, one feels, take a very distinct sensibility to find the sight of a naked Hoskins arousing, but the film is also very conscious about not portraying the female nudity in any prurient fashion.

But then the whole point of the nakedness is, as Hoskins says, that The Windmill was of a much more innocent time. "I don't think the tableaux would work now," he says.

"What was amazing about them was they were completely un-erotic. It was just beautiful. And funnily enough, when the girls stripped off and they're standing there, it was quite humbling.

"They weren't waving their bums around and jiggling their tits and all that number. It was art, and I don't think that would work today."