Husband-and-wife TV presenters Richard Madeley and Judy Finnigan have made their reputation covering everything from cookery to testicular cancer and Viagra, in a manner that suggested the whole thing was a very odd dinner party.

We haven't even sat down to start the interview, and already Richard and Judy are being very, very Richard and Judy. It is Saturday, the morning after their appearance on the Late Late Show, on which Eamon Dunphy and the Keane affair preceded them.

"The amount of time they had to discuss it," says Judy. "On British television you would never had so much time."

"Oh, you would," interjects Richard.

"No you wouldn't," says Judy.

"Oh, come on," gasps Richard. "If it was a major English footballer? If David Beckham had done something?"

It is the sort of endearing bickering - his bloody-mindedness, her slight despair at it - that is their trademark.

Every married couple does it, but nobody does it as famously as Richard and Judy.

For 13 years as hosts of ITV daily magazine show This Morning, they were not just presenters, but a couple sharing the low-points and high-points of their lives, and all the banalities in between. The show veered between the ordinary and the surreal. In between the cookery and garden slots, it ran such items as the first live Viagra trial, one experiment with orgasm cream, a graphic display of how a man should check for testicular lumps and three interviews with Tony Blair.

None of which would have been so sublimely addictive without Richard Madeley and Judy Finnigan.

They presented the whole thing as if it was a just a very odd dinner party. There was little we did not know about them, even if it was often clumsily revealed: usually by Richard, always to Judy's exasperation. Such as the time he breezily announced that he'd had "the snip". Amazingly painful, he divulged in a little more detail than expected.

But this is the man who, during his massively publicised 1990 trial for shop-lifting, would leave court every day, head straight for the studio and join the show mid-way.

She was more guarded, often seemed nervous, but was still surprisingly candid. She worked during bouts of clinical depression. Her hysterectomy was probably the most closely followed in media history. "Being on the telly doesn't protect you from going through those sorts of everyday experiences," says Richard, "I suppose we just acknowledge that."

They became objects of fascination for public and press alike. Yes, we can see what they're like on the television - but what are they really like?

"Out there, there is this strange fantasy, or suspicion, that there's a dark side," says Richard. "That the way we come across on the television is all well and good, but there's something schizophrenic about us. There has to be."

During the early years, the intrusion affected Judy most. "Everything came as an entity. So it sometimes seemed to me that we were being criticised not just for being on telly, and not just for having a show that people would like or hate, but just for being married. Everyone's entitled to their privacy, and I know we used to talk about our family a lot, but the quality of our relationship has never been in doubt. To have complete strangers speculating about what might be wrong behind the scenes was very hard."

They met when co-presenting a regional television show, a time when both were in marriages at the point of breakdown.

She was asked to introduce him to the ways of the office using the company's "parenting scheme", so she tapped him on the shoulder and announced, "I'm your mummy." A thousand future tabloid rumours were born.

"It's formed this whole f***ing industry of speculation in certain sections of the media," Richard says in a manner which suggests it irks him some days, doesn't on others. "The whole oedipal thing. Because there happens to be an age gap of eight years. Big f***ing deal. But that's just enough to get the flames going."

When he talks, Judy faces him. When she talks, he watches her. They are in Dublin to promote their autobiography, a chatty account of their lives on and off-screen, and the moments when there seemed little difference. If, like the tabloids and the public, their publishers were hoping to unearth dark secrets, they've looked in the wrong place.

"We were very honest with them," says Judy. "There's no kiss and tell stuff."

"What we tried to do with the book is show what it's like to have a foot in both camps. Camp Normality and Camp Weird," says Richard. It is filled with the sort of medical detail that fans love, and strangers marvel at. "It is an auto-biology."

The chapters concerning the shop-lifting charges - he left Tesco's with wine he'd forgotten to pay for - are the most interesting. "A charge as trivial as shoplifting, one that causes giggles, can absolutely destroy your life if it's untrue," says Judy. "It may be trivial, but there's also something ultimately tacky about being accused of that, as if you've tried to get one over on people."

"People ask if it was cathartic to write that chapter of the book," adds Richard. "I say no. The catharsis came when I was acquitted." Since then, the more tabloid moments in their lives have embellished the icon, rather than diminish it. The paparazzi shots of Judy in a bikini mocked her cellulite, but also confirmed her ordinariness. More recently, there was the astounding occasion when her dress fell down during a live awards ceremony being broadcast to millions. That it revealed a sizeable, matronly M & S bra, only endeared her to viewers even more.

"I was thinking about it the other day. It's astonishing because I do have a lot of nightmares, but I've never had one bad dream about it. So at some deep level, I must be OK with it."

"You think it would have cured her of those dreams where you go to work in your pyjamas or with no clothes on," adds Richard. "But it hasn't."

Their on-screen chemistry is one rival channels have desperately attempted to re-create, but without success. When ITV's new Controller of Daytime Television attempted to tamper with the formula, Richard and Judy left and signed a lucrative contract with Channel 4. Next week they begin the second series of Richard and Judy, an uncertain copy of This Morning that has struggled in the ratings. Meanwhile, the show they left behind has struggled badly. The controller has since lost her job.

Would they go back to This Morning? "I think that we'd got so cheesed off with the set-up at ITV that if you'd asked us about a year ago, we'd have said no," says Judy. "But things have changed at ITV and we always did love This Morning, so it would be foolish to say never."

"We've always been governed by contracts," says Richard. "All I can tell you is that our contract with Channel 4 runs out in a year from now. They seem happy with the show. It clearly hasn't become the huge, extraordinary thing This Morning became, but you can't do that twice in your career. But there's a quiet confidence about when we return. So we may go on to do more Channel 4 shows, but as far as This Morning, it's not beyond the bounds of possibility that we may end up going back." So, what are Richard and Judy really like? Well, you know that Richard and Judy on the telly? They're very like them.

Richard & Judy The Autobiography is published by Hodder & Stoughton, £17.99 sterling