It turns out she has come straight from a publicity shoot with "Uncle Terry" (Wogan, that is), with whom she is presenting Children In Need later this year. The coat is from the high street and the bags bursting with everything a girl might need as she hops from presenting jobs to photo shoots to a coveted spot on Jonathan Ross's sofa, where she spent last Friday evening.

The interview with Ross went out just hours after Cotton's audience with Prince William and Prince Harry was broadcast. She made headlines earlier this year when it was announced the princes would discuss their late mother on camera, for the first time, with this 25-year-old music and reality TV presenter. The American NBC network also secured an interview with the princes, with their experienced news anchor Matt Lauer treating the occasion with more gravitas.

The BBC interview is a precursor to today's Concert for Diana at Wembley Stadium and Cotton was adament she didn't want to do a Martin Bashir-style Panorama interview. "I wasn't there to dig dirt and be the bad guy. That's not what the BBC wanted. If they'd wanted something more journalistic and hard hitting they would have got Huw Edwards.

"They wanted something which was going to be compelling and compassionate but still fun."

She has just watched the interview for the first time and is pleased with the result. "I think they [the princes] did drop their guard and were very natural. They spoke about their mother for the first time ever publicly; it was a very special thing to hear."

Cotton is fascinated by the royal family and says she has always been interested in the work the princess did for charity, even though the TV presenter was only 15 when Diana died. Cotton first contacted Comic Relief six years ago and has since visited Kenya with them and still exchanges letters with a young woman she met out there. She was a presenter for the Live 8 concert in Hyde Park in 2005 and is a youth ambassador for Macmillan Cancer.

Less worthy was the ITV celebrity reality show Love Island, which Cotton presented last summer with Patrick Kielty. The show's poor ratings coincided with the then chief executive of ITV, Charles Allen, stepping down.

For Cotton, who began her presenting career on the Disney Club aged 16, the criticism was water off a duck's back.

"I can safely say that doing Love Island was the best three months of my life. Living in Fiji, it felt like I had no responsibilities. All I had to do was get up, go to work and lie on the beach.

"It doesn't bother me [that the ratings were bad].

There's always going to be another project that I can get my teeth into. Hopefully, if I keep working hard, there will be new stuff to replace the ones that don't come back."

In fact, while ITV has axed Love Island, it has designed a new dating show especially for Cotton and her best friend, presenter Holly Willoughby. The pair are styling themselves as the Trinny and Susannah of the dating world and hope to fix the love lives of six singletons in the show, which airs in September.

She also presents a weekend show on BBC Radio 1 and recently began filming The Xtra Factor, after losing out in the battle to present the main X-Factor show to Dermot O'Leary.

"Dermot is perfect for the job, " she insists. "Having a boy made sense if they wanted to change the show. I suppose they wanted to flip it on its head and I don't think I was right for that as I am a blonde girl presenter and they stick you in the same category."

To get to where she is now, Cotton missed out on the student lie-ins . . . "a teenyweeny sacrifice" . . . and balanced presenting jobs with one A-Level in art at college in northwest London, where she grew up with her "very chilled out" signwriter father, a mother who "loves alternative therapy and reiki but is by no means a hippie . . . in fact she's uber-glam" and younger brother Jamie, "who doesn't give a crap what I do".

She talks at speed and her huge green eyes dart in every direction, betraying the restless, fidgety nature she admits to several times. Very little makes Cotton pause for thought, but she struggles to put her finger on where her fierce ambition comes from. She says her parents were never pushy but always supportive and that once she realised she was good at dancing as a young girl, she wanted to become better at it. When her relationship with Peter Brame, a Fame Academy contestant who Cotton dated for two years, came under scrutiny because of his drug issues, she called time on the relationship very quickly.

Brame responded with a spread in a Sunday newspaper chronicling their sex life.

"It was upsetting, but you have challenges to face and then you just get on with it.

I don't think anyone was giving me much pressure [to split up with him]. I put it on myself because my job's more important than anything. I knew my job was more important the second I started off in that relationship."

Batting off rumours that Prince William asked her on a date, Cotton is happy with her model/chef boyfriend of 10 months and says she would rather stay in with him and her cats than choose a dress from a selection lent by top designers and flirt with Jonathan Ross. Last weekend she went to Glastonbury . . . she had never been before; ever since she has been old enough to attend she has found herself working that weekend.