Best-selling author Jilly Cooper has been talking ingenuously about love, jealousy, betrayal, trust, hurt, sex, toyboys, mistresses, money and affairs. ‘I always feel God is up there peeling a heavenly banana skin to throw under my feet,’ says Jilly, who once appeared to have it all and had the image of a frothy party girl.

‘Whenever I’m happy, I always get terribly excited. You might as well be excited because life’s such a bugger. But whenever I’m happy, I always start to shake waiting for something bad to happen.’ She looks around. ‘There’s probably a tiger lurking under the piano.’

She says it’s silly, because life is good for her at the moment. Her last book, Polo, has just come out in paperback, Riders is being made into a movie and work is going well on The Man Who Made Husbands Jealous, about the havoc wreaked among wives by a toyboy.

However, her mother is ill, her best friend died last year, and she has been bandaging her wounds and rebuilding her marriage since publisher’s secretary Sarah Johnson went public almost two years ago about her ‘gloriously passionate’ eight-year romance with Cooper’s husband Leo. We are sitting in her beautiful Cotswold house, decorated in arty and bohemian style, filled with pictures and books. Outside, the bluebells and cowslips are out, and the bronze relief of angels in situ is on one side of the house and a totem pole of an owl sitting on a pile of books guards the front gate. ‘Never mind the dog. Beware of the owner,’ reads the wooden sign on the porch. Who’s the owner? ‘Debatable,’ says Jilly, the blockbuster earner, laughing hugely.

She says that when she goes to London now, labourers on building sites yell: ‘How’s your marriage Jilly?’

‘I scream with laughter and we have a good old giggle about that,’ she says. In reality, she is loath to talk about this painful subject and we reach an early impasse. ‘No, I can’t talk about it. I can’t.’ On election night, she was photographed at the Conrad Black party with Jack Profumo. ‘I fell on his neck and he fell on mine and I said, ‘Does it ever go away? Will the press ever leave us alone?’ And he said, ‘No.’ ‘It’s awful . . . I just think God, Christ, what hope have we got if it keeps getting raked up in the press. Leo goes berserk about it, understandably. He’s trying to rebuild his life and so am I.’ Much of the time when she is talking, she pulls her hand through the top of her hair in a gesture of distress.

How have they worked on rebuilding trust? ‘I don’t think we have. I don’t know that you can.’ Does she still feel she wants to make her marriage work? ‘Yes. But I can’t talk about this. I’m sorry.’ On being pressed, she continues to talk, trying hard to be accommodating and truthful in very tricky circumstances.

‘The play Othello says it all about jealousy. Every trifle is blown up. It gnaws. You start thinking someone is catching an earlier train to make a phone call from the station. You twist everything. Jealousy is like vomit, you can’t keep it down.’ Is that all in the past now? ‘Things get tainted by it.’

Rebuilding her marriage has been tough and her sadness is palpable. She says she’s easily cast down. ‘It’s very difficult rebuilding something at a distance.’ Leo is a small publisher, away in London three days a week. ‘I’m alone down here and the imagination goes berserk. Solitude is bad because one starts to brood and if you’ve got a writer’s imagination . . . I’m charting every emotion, writing everything down. That’s how writers save themselves. I think I’ve become more compassionate.’

She’s coped with her hurt mainly with her (self-professed) workaholism. ‘I work horrific hours, from 10am to midnight. It’s like a drug. If I’m in a bad mood, I have a fix of producing half a chapter which I’m happy with and I’m high as a kite when I come back. I don’t ever ring people up and say, ‘God I’m miserable.’ Occasionally if people ring up they get an earful.’ Sometimes she doesn’t go out for months on end. Laughingly, she says that she suffers from ‘hermititis’. ‘You lose any sense of your identity as a woman,’ she has said.

She is wearing a jumper decorated with daisies, and black jeans. At 55, she is remarkably youthful-looking and pretty, with cascading Seventies hair and the famous gap teeth. Photographs of two of the loves of her life hang from her neck in a gold pendant: Hero and Barbara, the dogs (‘the dawgs’) with whom she admits an overly symbiotic relationship.

Slight and slender, Jilly has dieted off 8lb this week and most of the time nurses her coffee mug with chilly hands. ‘When I’m very upset, I stop eating completely. Otherwise, if I’m upset I just go straight to the bread bin.’

She says she turns her setbacks into challenges. ‘I blew dandelions this morning to see whether my toyboy novel was going to be a success. The dandelion said no. That’s good because it means I’ll get back to him (the toyboy) and really look after him.’ She reacted with similar fortitude when she didn’t receive an author award she had hoped for last year. ‘I couldn’t cry my eyes out because I had to go back to a hotel with Leo and I didn’t want to keep him awake. But I suddenly looked out of the window and thought, ‘F*** it, my next book will be better’.’

How does she now see herself sexually? ‘I don’t think of myself as a wildly attractive person sexually. I haven’t got enormous confidence on that front,’ she says, then laughs and says she hasn’t yet reached that age when women cut their hair and paint furniture.

She has asserted her independence after three decades of marriage by starting to learn to drive and looking for a house in London. Would life have been easier if she hadn’t been the main provider? ‘I think it would have been easier for everybody’s sake.’

The effect of Leo’s affair on her children has been devastating, but they have stood by her and been immensely considerate. ‘They’re much nicer than I am. Much braver, not as frightened and more secure, I hope.’ She doesn’t worry about their leaving home. ‘I have a great family waiting for me in the gazebo (where she writes).’

Felix and Emily were babies when she adopted them. ‘All I feel towards their natural mothers is the most passionate gratitude. I couldn’t have produced anything better myself.’ Jilly says she has come to terms with not being able to have children. ‘I had my ectopic pregnancy, my flicker of fertility. Almost from the moment the gynie told me I couldn’t produce, I was devastated, but I started to write. That was my reward.’ She doesn’t know if her children want to look for their natural parents. ‘They haven’t told me they do. But they may want to in their hearts. I might be upset if they went looking. But if they just wanted to see what their parents looked like, I wouldn’t mind.’

Her own father, ‘a solid, honourable man’, died in 1982. ‘It was awful. It was a bad year. He died of cancer, Fortnum my dog died, we left Putney and I left The Sunday Times.’ She calls her mother ‘my joy’. And she has a ‘lovely, glamorous’ older brother.

Her own childhood was idyllic. She quotes Margaret Astor. ‘If you have been sunned as a peach on a southern facing wall all your childhood, you are very conscious of loss of warmth.’ She was ‘distraught’ when she went to boarding school, and she tries now, she says, to recreate that sunshine by being nice, sweet and polite to people.

Disarmingly, she gives me a kiss on arrival and a hug when I leave, although we have never met before. She wants to control the outcome of the interview by making you into an instant friend, and taking you into her confidence and telling you off-the-record secrets. But she is also very sensitive (both easily hurt and perceptive), extremely clever, kindly, witty and well read. Ask her to describe herself and she says she’s dotty, wet, emotional, sulky, fearful of confrontation, underconfident, shy and disorganised, adding that she’s Pisces.

She’s terrified of confrontation. ‘I’m getting better at standing up for myself. But I always feel terrible about myself afterwards and I always shake.’ She rows only occasionally with Leo and never in public. How do they communicate angry feelings? Do they sit down and talk in a grown-up way? ‘No. We don’t do that either.’ She laughs.

‘There must be an awful lot of very bumpy carpets in this house from things being swept under them. We don’t have conversations about life. It’s all very English boarding school, jokes rather than talking.’ Isn’t that lonely? ‘I think at a time like this, people tend to walk on eggshells. The very sad thing is that you get two people who are frightened of each other because they know they can hurt one another.’ She cradles herself with her arms. ‘People oughtn’t to be frightened of each other.’