Why is Judy unhappy?

The studio at Cactus TV, where the Richard and Judy show is recorded live every day most days of the year, is a whizzy little place. It is full of young, attractive people buzzing around brightly lit endless corridors. It's all very "TV" - fast, smiley, young, strange. Someone rushes past me carrying a tray of cooked snails. Two tiny puppies are gambolling around the office. One stops to defecate next to a filing cabinet. No one seems to notice. Suddenly, the televisions placed round the studio flick on. It's 5pm. And, as if from the middle of nowhere, up pop the beaming, reassuring faces of Richard and Judy. Everyone, bar the naughty puppies, stops and sits and breathes one huge, communal sigh of relief.

What is it about Richard and Judy that makes everyone feel so good? They are so universally loved, so critically acclaimed that they are almost untouchable. Three years ago, when they quit ITV's This Morning after 13 years of makeovers and fashion items, the knives were out. No one knew what they thought they were doing, haring off to make a late afternoon show for Channel 4. But, after a few patchy weeks, the show took off and now, more than two years in, they pull an audience of 2.5 million - which is way more than they did at ITV.

Part of their appeal, maybe, is the fact that they turn live television into an art form, even if last month they were criticised for asking two couples to have sex as part of an exercise experiment. Under their guidance boring nonentities turn into scintillating raconteurs. One of their guests today is a Canadian man who sticks his head in tigers' mouths. "Gosh," says Judy Finnigan, looking genuinely shocked at a piece of film footage of their guest "roughhousing" with a tiger. "That's very exciting. You must have studied tigers for a long time to know how to relate to them so wonderfully." And, all at once, their guest appears knowledgeable and exciting rather than completely bonkers.

Once the show is over - no fluffed lines, consummately professional - we go back to Finnigan's dressing room. There is wine, water, goody bags, everything you could ever ask for. Hollywood guests apparently love coming on the show because of the wonderful gifts they get. " And because of us!" says Richard Madeley, pretend-affronted. "We've been in the business 16 years. I hope people come on the show because they think it's good. I mean, we're very hospitable. If guests want to stay on afterwards then we welcome them, don't we Judy?"

He turns to his wife. "Yes we do," says Finnigan, rather tiredly. "We like meeting people because we enjoy doing new things and this show allows us to do many things we've never tried before on television."

"We're doing a book club!" says Madeley, nodding his head enthusiastically. "We review 10 books that we've shortlisted as being a good read and then, at the Book Awards in April, one of them will win the Richard and Judy Best Read prize." "The viewers vote on which is their favourite," adds Finnigan.

"We've already done Joseph O'Connor's Star of the Sea and the sales rose by 350 per cent," interrupts Madeley. "We're amazed at that because people kept saying books don't work on TV but they do, don't they Judy?"

"Yes," says Finnigan. "Like I said, I really enjoy doing things we've never done before." Madeley raises an eyebrow. "I like doing things we've never done before, too," he chortles at Judy. "Oh Richard," she says.

This is typical Richard and Judy. By common consensus, Richard is the youthful, chatty, mad, vague, off-the-wall one. He's tall dark, slim, attractive and from a middle-class background. He's well-known for revealing too much about their personal life, saying things like "the rhythm method doesn't work for us, does it, Judy, because your cycle is so unpredictable".

She's the opposite; older, blonde, not very slim. She's quieter, more intense, more nervous and from a working-class family. She spends a lot of her time fiddling with her hair or clasping and unclasping her hands. While he chats and says this and that, she sits and thinks and then gently reels him back in before she asks her own thoughtful, sometimes more pertinent, question.

Yet there is something else about Judy Finnigan. She's very sympathetic, very empathetic. When they come off air she looks absolutely exhausted whereas he is as high as a kite. Her hands shake when she passes me a glass of water.

"Where's my special glass?" she asks a helpful assistant who has followed her into the room. She starts looking upset and nervous. The assistant passes her a glass full of lord knows what - ice, lemon, tonic, maybe.

"Are you tired?" Madeley asks her. "She always gets so involved," he says to me. "I sort of glide over the surface but Judy gets emotionally close to people." It's something she has talked about in the past, her incapability to pull back. "I find I can't help but get involved," she says. "I don't know if it's a woman thing or a me thing. Every guest we have I want to talk to and really listen to what they have to say. But it means I get more tired than Richard. I feel more drained."

She's the only one of the two who, occasionally, talks about not working. "I love doing live TV," says Finnigan. "You have to react quickly, look at the news, be current and then, at 6pm, it's all over. We go home and see our children (Jack, 12 and Chloe, 13) and then start again the next day." Then she says: "I didn't think I'd still be on television after the age of 50. I'm 55 now. I still enjoy it but sometimes I wonder when it will be over"

"What will we do then?" asks Madeley, in a slightly incredulous tone, as if not believing that day will ever come. "Oh, I know what I'll do," says Finnigan. "I'll go to our house in Cornwall and relax." "Relax?" says Madeley. "Relax," says Finnigan sternly.

In a way, she probably has more right to call the shots. Finnigan, for reasons which actually escape me, has been the butt of most of the criticism of the couple. Much is made about the fact that she is eight years older than her husband and that, as she ages, he seems to look younger and younger. Then there was the fact that she "stole" him, which is rather unfair as they were both married when they met nearly two decades ago at Granada Television.

She was married to journalist David Henshaw and has twin boys Dan and Tom, now 25. He was married to Chelsea Girl deputy manageress Lynda and had already been unfaithful. "I got married young," he says. "What more can I say?" In their eponymously entitled autobiography, much is made of the fact that a) Judy was very lonely as her former husband was away a lot and he also didn't want any more children and b) she suffered terrible guilt over her affair with Madeley.

"I think I am a typical woman," says Finnigan. "I was very attracted to Richard and he was obviously attracted to me, but I felt very trapped and didn't know what to do. Richard didn't feel that way. Men don't question themselves as much as women. They don't feel guilt in the way we do."

Finnigan tells me she thinks the reason why they are so successful is that they mirror most other couples' lives. "I meet so many women who tell me their husbands are just like Richard!" she says. "In a way they play the role I do; mother, lover, carer.

"When we first started at This Morning, we couldn't go to our daughter Chloe's first nativity because we were working. I was devastated by that, whereas Richard wasn't." "I was," protests Madeley. "Not in the same way," retorts Finnigan. "I'm a man!" he wails back.

In many ways she has probably hit the nail on the head. They seem like a normal couple with their little admonishments and on-screen tiffs plus the revelation that they buy their wine at Tesco (he was accused and acquitted of shoplifting at the supermarket in 1990. He claimed he just "forgot" to pay for it, a defence which, having met him, is all-too believable).

They've also had their fair share of usual, but painful, ups and downs. He's had a vasectomy, she's had a hysterectomy plus one miscarriage and a still birth, and there was the seminal moment on live television when her blouse buttons opened to reveal a vast expanse of bra. "Oh God, that was awful," she says, "but not anywhere near as awful as the other stuff."

Rumour has had it that he's unfaithful, she's an alcoholic, they're S&M freaks with a dungeon in their basement. "Crazy, isn't it?" says Madeley. "We call it the Serpent-In-Paradise syndrome. People cannot believe that we are happily married and good workmates."

Of course they don't, I say. It's pretty unbelievable, almost abnormal. What if they've had a horrible row? "We're so used to working together," says Finnigan. "It's so much part of our lives I don't think I can imagine it any other way." "Believe me," says Madeley, "there are no dark secrets going on here." Well, if that's true - and I have no reason to doubt that it is - why does Judy Finnigan appear so unhappy? She looks as if a large dark cloud has settled on her shoulders. In the past she has talked about how she is more prone than her husband to self-doubt and bouts of depression. "My father was like that," she says. "My mother wasn't at all. She was very practical and can-do but he was more melancholic, and I think I've inherited his genes."

She says she had a hysterectomy because her mood swings became so intense. "I was off work for a bit," she says. "That's when everyone either thought she'd left me or gone to a drying-out clinic!" says Madeley.

"I actually found all that very hurtful," says Finnigan. "However hard I try not to care, I find that I do."

Their guests, including the mad tiger-head man, are waiting for them in the hospitality suite. "Mustn't keep them waiting!" says Madeley. Finnigan gamely gets up, looking as though she would rather be anywhere but here.

As they leave she stops and says to me, rather thoughtfully: "I think the reason why this all works so well is that he's an attention-seeker and I'm an attention-giver. He floats above the world and I ground him. I look after him really." "Come on!" yells Madeley. She gives a little shrug and walks off.

But half an hour later, when I've finally shut the door on the puppies and have negotiated my way out of the corridors, I see them in the car park. Richard Madeley has one arm around his wife, tenderly guiding her across the paving stones. In the other hand he is clutching a plastic cup half full of white wine. When he sees me, he salutes me with it. I don't know why, but it made me laugh.