Naomi Campbell is not angry. The outbursts, the run-ins with the law, the tantrums - they have nothing to do with anger, she insists, but instead are born of frustration - at the lack of diversity in fashion; at the view that black models are just a passing trend; at her contributions to fashion and charity being often overlooked.

“I'm not saying I've always used my frustration in the right way,” she says, “but my gut instinct is to keep women of colour out there whether I'm still in fashion or not. I'll be very happy when I'm 55 years old to pick up a magazine and see a lovely spread with a black woman. Then I'll know that I didn't work for all these years only to see it go backwards.”

Over jasmine tea at the Dorchester, we marvel at the absurdity that she is now finally “on trend” by virtue of her skin colour. With America considering the election of its first black president, Italian Vogue's first black issue proving a sellout and spawning much analysis of the lack of diversity in fashion, and the French designer Sophie Theallet's decision to send only black models down her catwalk in New York last week, it seems that it has never been more fashionable to be black.

But Campbell, the first black model to grace the covers of French and British Vogue and often the lone ethnic-minority face on the catwalk, is quick to point out that it wasn't always this way.

“Last year New York was the worst of all the fashion-week shows. They didn't use many black models at all,” she says.

For decades, fashion editorials and catwalk shows have preferred to focus on an extremely tall, thin, young, white ideal. The received wisdom (confounded by the success of the recent Italian Vogue issue) was that “blacks don't sell”. In New York, a survey this year found that just 6 per cent of the available catwalk slots were given to black women.

So for 20 years Campbell felt that she couldn't retire. But now she can, she says, after listing several black models, such as Jourdan Dunn and Tyra Banks, who have appeared on major magazine covers in recent months: “This time they [designers and editors] have stepped it up. I feel positive. That means that I can go soon.”

This increased diversity will be reflected at her annual charity fashion show and auction, Fashion for Relief, in the British Fashion Council's tent at London Fashion Week tonight. The event is in aid of the White Ribbon Alliance, which campaigns for safer pregnancy and childbirth worldwide, and will feature eveningwear by Alexander McQueen, Dolce & Gabbana and Vivienne Westwood, among others, modelled by celebrities from the worlds of fashion, music, sport and film, all chosen by Campbell and representing an array of ages and ethnicities.

It irritates Campbell that some people view her charity work as merely a ploy aimed at gaining public redemption: “Sometimes they are like, oh, you need to get out there and do what Angelina Jolie's doing - and I'm like, I've been doing it, I just care to keep it more discreet. What she does is incredible but I choose to do it in my way.”

It is hard to imagine that this smiling, chatty and sometimes vulnerable woman is the same one who swore at an airline pilot and attacked police while being removed from a plane in handcuffs in April. But the fickleness of the fashion world is clearly one subject that still arouses strong feelings in her: “The black issue of Italian Vogue shouldn't make it briefly fashionable to be black, then unfashionable again,” she says.

Can any amount of aggravation from the industry in which she works excuse the much-publicised bad behaviour that has got her into trouble, though?

“I've done some things that were plainly just not right,” she admits, “and I take that on the chin 100 per cent. There have been many frustrations. But I don't like using excuses. You know, if I did something wrong, I did something wrong - and I'll pay the price for it.”

That was exactly what she was doing last week when, having admitted the “air rage” assault charges, she started her sentence - 200 hours of community service at a shelter for the homeless in East London.

“I have learnt - I am learning, I should say, not to be provoked,” she says. “But if someone insults me, I'm still going to defend myself. I don't take good to racial insults...

“I know that I am blessed - but there is always scope for change and improvement. Obama is for change, and I really hope he wins - let's paint the White House black.”

Tickets to Naomi Campbell's Fashion For Relief for the White Ribbon Alliance are available through www.ticketmaster.co.uk

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