"I know it sounds clichéd," she says. "But I've had 20 years of fame and fortune, and I feel that I have a right to an opinion on what it is and what it isn't. All everyone is obsessed about at the moment is being a celebrity. I'm saying that's bullshit and who knows better than me? Before it happens you have all kinds of notions about how wonderful celebrity is and how much joy it's going to bring you. Then you arrive...
"In America, more then any other place in the world, you have the freedom to be anything you want to be. Which is all well and good, but it only works if you have a value system and we seem not to have one anymore. It's whatever it takes to get to the top, and that's what you gotta do.
"It's the allure of the beautiful life," she continues. "Look like this you're gonna be happy. Drive this car you're gonna be popular. Wear these clothes and people are gonna wanna fuck you. It's a very powerful illusion and people are caught up in it, including myself. Or I was. "
With varying degrees of success Madonna continues to flirt with acting. Last year husband Guy Ritchie directed her in Swept Away, a remake of a 1974 Italian sex comedy. It was savaged by critics who reserved special venom for Madonna's performance. A commercial flop in the US, it will go straight to video in the UK later this year.
"Everyone in England has slagged it off without having seen it. Isn't that beautiful? Don't you think that's absurd? But I think the knives were going to come out for Guy anyway, even if he hadn't ended up with me. He had too much success with his first two films. That's how the media is: eventually they have to pull you down."
So why do you carry on?
"Because I enjoy acting it's fun. I don't give a shit about what people say about it or about my music."
But clearly you do.
"But you can't let it influence the choices you make," she says, retrieving a crumpled and obviously well-used tissue from her jacket pocket. She carefully lifts it to her nose and blows, then has a quick look to see what she's deposited before dropping I onto the table.
"You must be careful what you read," she admonishes. "Nothing is what it seems."
This is particularly true, she says, of the acres of newsprint devoted to what her and Ritchie get up to when they're living in the UK. The Daily Mail, for one, ran a scathing portrait - courtesy of anonymous sources - of their life at Ashcombe House, the stately home in Wiltshire they bought in September 2001. According to the Mail, Madonna spent several thousand pounds trying, and failing, to learn how to shoot. She also had an unsavoury run with ramblers keen to exert the right to tromp over Ashcombe's fields. "Get off my land!" responded Madonna. Allegedly.
"I didn't have a go at ramblers! Jesus Christ!" she groans. "I didn't have a go at anybody. They're pissed at me because I left England. To tell you the truth when we brought Ashcombe we did think, oh, there's a path, people are going to be bothering us all the time. But no one did. I haven't got anything bad to say about ramblers."
It was also reported that you suggested our climate was crap and our houses too damp.
"The irony of all that stuff coming out in the papers about supposedly slagging off England is that all I've done since we've been here is say, Let's go back to England - it's so boring here."
Do you ever want to take off and disappear?
"Me and Guy thought about it. But of course I'd never do it. I'm too responsible."
Look on the bright side, you could be Michael Jackson.
"I haven't seen that documentary [Living With Michael Jackson], but it sounds disgusting, like he [Martin Bashir] exploited a friendship. Publicly humiliating someone for your own gain will only come and haunt you. I can assure you, all these people will be sorry. God's going to have his revenge."