How can years of love and affection dissolve overnight into vitriol and disdain? Hettie Judah hears some sour stories
It doesn't take a Mori poll to work out that Grandpa Jagger has won the "Unreconstructed Male Bastard of The Week" award by a landslide. Frankly the form takes some beating; after years of philandering he's now trying to deny the validity of his marriage to Jerry Hall in a bid to keep her hands off his cash. Hello! magazine fans and their ilk have been mentally huddling round Jerry like a 17-year-old girl gang cooing "you're too good for him, love", "I always thought he was a nasty piece of work", "go on darling, you give him what-for" and all the usual invaluable insight and wisdom that tends to emerge at such times.

What seems to have been conveniently forgotten is that these two people were, until very recently, regarded as being in love. Sure, Mick and Jerry have split up before, but when they got back together it was generally seen as "a good thing" because they had "something special" that couldn't be destroyed by extracurricular sex and bad behaviour. Jerry didn't stick it out with Mick for 20 years because she was so dense that it took her that long to realise that he was a scumbag. She actually liked the ol' dirty bastard; and he certainly wasn't sufficiently sick of the sight of her to put him off legitimate marital sex; remember, please, that these people have a very young baby. Two decades of mutual sexual attraction is not something to be sniffed at. Until last week, these two people were sufficiently fond of each other to want to make a go of their relationship.

Looked at in this way, Mr Jagger's behaviour over the past few days seems particularly disturbing. One day he was, at the very least, fond of the woman, and the next he appeared to be doing everything in his power to hurt and humiliate her, despite the fact that he was technically the guilty party. Yet his behaviour, even away from the mad world of the rich and famous, is by no means unusual.

Rachel, who at 42, is the same age as Jerry Hall, is currently in the middle of classically gruesome divorce proceedings. Two years in, she says that she feels in a constant state of shock; not at the breakdown of her marriage, but at the viciousness of her husband's legal attack on her. "Of course, I was deeply upset after he told me about the affair," says Rachel, "but when I went and got the children and explained what was happening, I remember very clearly hugging them all and saying, `Remember that Daddy is a good man and he will take care of us; no matter what happens he still loves us all; he's going to try as hard as he can not to hurt us; it's all going to be OK'. The weird thing was that I really believed that is what would happen; after all, we were a family and he loved his kids. Then suddenly he just seemed to change, and it became more like a war between us. All our love seemed to have been forgotten."

"It is very common to behave badly towards people we have wronged," says social psychologist Robin Gilmour. "There may be guilt for breaking up a lasting relationship and sometimes that guilt gets twisted into aggression; sometimes we attack people who make us feel guilty even if it is deserved; the person who is wronged becomes the victim."

Denise, in her twenties, encountered more immediate problems when she split up with Scott, her boyfriend of over three years. "We weren't living together, but at the time he used to stay at my place most nights. One night we had a massive row, and basically split up. Within the space of half an hour he completely flipped. I told him to leave the flat, but he wouldn't get out of my room, so I went to sleep on the sofa. The next morning when I went into my room to sling him out I discovered that he'd cut up my new suit; it was pure spite, as if he had been looking around the room trying to work out what was the most hurtful thing he could do. A fit of rage is understandable, but this was pretty cool and calculated."

Such stories are familiar stuff, but how much is the speed of emotional change real, and how much does it depend on the storyteller's perspective? According to Robin Gilmour, a change of this speed rarely happens: "It may seem more sudden to one party than the other. There may be elements to the breakdown that one half is not party to, thus to them it looks sudden. But from the other partner's point of view, it has been bad for a while; much is in the perception or the account of one of the partners."

Often within an apparently stable relationship there are problems that the couple collude in suppressing. They do this in the interests of staying together but this creates an artificial calm that often leads to a dramatic emotional swing once the move has been made to end the relationship. Paul, 29, split up with Helena six months ago. Although they moved into separate flats, they both still live in the same small town and frequent encounters are unavoidable. "It's not like either of us was sleeping with anyone else," says Paul. "The decision to end it was a mutual one, and I was looking forward to staying as mates. But from about a week after she moved, it suddenly became like I was some kind of evil bastard. When we saw each other, she just couldn't resist making nasty comments. It was as though she was trying to knock me down a bit."

Once the illusion of maintaining a relationship is shattered, all manner of unpleasantness can erupt, apparently out of the blue. It's a phenomenon that many of us have seen - a potent cocktail of wounded pride, guilt and long-buried resentments surfacing with a bang. It is difficult to imagine Mick and Jerry spitting profanities at one another over the caviar counter at Harvey Nicks, but I'm sure Ms Hall will give as good as she gets when it comes to insult and injury. Ladies and Gentlemen, the fuse has been lit. Please stand well back from the fireworks.