Davina McCall: The First Lady of chat

Hyper-emoting through umpteen Big Brothers has won her the ultimate prize, her own BBC chat show

Everyone loves a bad girl gone good. The upwardly mobile trajectory of a former druggie, alcoholic, sexually indiscriminate female tearaway is meat and drink to celebrity magazines and tabloids. You only have to look at Sharon Osborne or Drew Barrymore to see that a public clean-up act can pay dividends.

And so it is with Davina McCall, the queen of Big Brother, who has just signed with BBC1 to present a pre-watershed, mid-week chat show - the old Parkinson slot - for a reputed £1m.

McCall's rise from her days of boho degradation is the archetypal tale of a tough totty who became the babe on the box. Trailing her history - which she has no shame in revealing to every tape-recorder set in front of her - she has a kind of wham-bam energy that comes right out of the television screen and into the faces of the millions of viewers who tune in to BB. She doesn't so much wear her heart on her sleeve as her entire personality. Moreover, she is generally considered to possess the highest EQ (excitability quotient) on TV.

At 38 going on 18, she has a cross-generational appeal that the BBC chiefs undoubtedly hope will turn Davina, her chat show, into a distaff Wogan. And given her credentials, it is extremely likely she will achieve this unless some unforeseen calamity (like poor viewing figures) occurs.

It is the combination of spiky, you-wanna-shag-me-get-in-line sexiness with her enthusiastic embrace of motherhood that gives her the edge over her rivals. She can now, she says, afford to be a bit square, a bit Gloria Hunniford, though I doubt that she will make the full transition to Oxo mum. Mercurial and flamboyant, she combines the distillation of loudmouthed ladette with touchy-feely new age comforter. Physical and tactile, she can work a crowd like few others, oozing empathy like a virus, whipping up the rabble to near hysteria and offering solace to those dejected and ejected from the BB house. This facility to switch moods at high speed has led some of her detractors to claim she has all the depth of a puddle after light rain.

Davina is unrepentant. She is impervious. She is street smart and knows that the best way to confound the critics and defray those who seek her downfall is to reveal absolutely everything about herself. It's an old trick, one practised particularly by former addicts, and amounts to a kind of therapy through a continuum of confession.

Of course, there are those who will never see the point of her, sourpusses who believe that she is a monster epitomising the nadir of culture, wedded to the Frankenstein of reality TV. For others, she is the celebrity's celebrity, the iconic airhead with a sexy mouth, architectural eyebrows, an inquisitor's nose and a now-you-see-me-now-you-don't hairstyle. The reason she is a television natural is precisely because she provokes such extreme reactions: you either love her or loathe her. Indifference was never a criterion for fame.

She was born Davina Lucy Pascale McCall in London on 19 October 1967 to a French mother, Florence, and an English father. Mum was, according to the gospel of St Davina, "a gorgeous Sixties chick" who ran the Yves St Laurent boutique in Knightsbridge, while dad was a sales rep for Jaeger. Three years after her birth, her mother fled back to Paris and her father sent her to live with her grandparents in Surrey where she became, in her imagination, the sixth member of Enid Blyton's Famous Five.

At 13 she returned to live with her father and his new wife in west London, where she attended Godolphin and Latymer School. In common with many teenage girls, anorexia beckoned and she shrank down to six stone.

At 18 she moved to Paris and plunged into a misspent-but-by-no-means-wasted period of alcohol, cocaine, sex and miscellaneous debauchery. Her work as a singing waitress in the Moulin Rouge began to suffer as a result of her up-all-nightclubbing lifestyle during which, she has admitted, she was "a complete mess".

"It was party-messy not down-in-the gutter-messy" says a friend from those days. "Like a lot of those middle-class girls who went on to make something of themselves you never really worried about the fact that she would eventually be all right."

Salvation came in the unlikely shape of a former boyfriend, Eric Clapton (no stranger himself to substance abuse), who gave her a good slapping - figuratively speaking - and encouraged her to try for a job at MTV in 1992. "If I hadn't bombarded MTV with audition tapes and got a job there through sheer bloodymindedness," she said in a recent interview, "I'm not sure what would have happened to me."

It was on MTV that she honed her presenting, on-camera people skills, in Most Wanted. In 1996 she was presenting Streetmate, Channel 4's matchmaking programme, and in 2000 she got her biggest break by becoming the face of C4's Big Brother.

Not that it has been all wine and roses. ITV's 2004 show Love on a Saturday Night - a putative rival to the BBC's Blind Date - proved a stinker. Similarly, The Real Holiday Show, God's Gift and He's Having a Baby sank without trace, a trail of non-starters that would have sent many neophyte presenters back to the job centre. It is a measure of Davina's resilience and self-belief that she survived to squeal another day.

As if that were not enough to make one grind one's molars with resentment, there is the incalculable smugness of her domestic life. Following a brief six-month marriage to actor Andrew Leggett ("just wrong") she married jolly super Pet Rescue presenter Matthew Robertson and has produced two daughters, Holly, three, and Tilly, 18 months. Ever one to spot a publicity opportunity, she became an ecstatic mother, recovering her figure in double-quick time and then providing an exercise video to capitalise on her success. Plus, she went "birth simple" and declared that she was hooked on the whole messy business. The deliveries of her children, she claimed, were "orgasmic". She said: "They knocked spots off any drug I've ever taken. When those babies popped out, I wanted to stand naked on the highest mountain and roar with pride."

If ever her TV career falters, she claims, she would actively entertain the idea of becoming a midwife, to share the orgasmic experience of birth with other, less enlightened, souls. Yes, the yuk factor is high with Davina McCall. There is a shameless complacency, an irrepressible smugness that makes some people want to commit violence. But for many others she is a beacon, an exemplar of the possibility of achievement.

Nothing, it seems, succeeds like excess. And the gloriously excessive Davina McCall is now in serious danger of having it all.