'WE get two or three a month,' the women's aid worker told me. 'It's quite common.'

I was horrified. Battered wives were old news, but battered mothers . . . Teenagers, I thought. The adolescent male, a cocktail of aggressive instincts. I shuddered and thought of my own son, who at nine and a half was everything I could wish for: intelligent, sensitive, funny, affectionate, kind to hamsters and small children. I little thought that within months of hearing about battered mothers I would be one myself; that the little boy everyone liked would be punching and kicking me as I lay on the floor sobbing for mercy.

It happened at bedtime. Yes, I know, we've all seen grisly behaviour at bedtime and even been guilty of a bit of it ourselves. But this was something else. It began at 9pm and confrontation came at about 11pm. I lost my temper and told him to get to bed. 'Just do it]' I remember shouting. 'I'm fed up with you]'

But being told what to do was obviously not on the menu for Tom that night. 'Piss off, you fucking bitch] I hate your guts]'

Outrage is hardly the word for what I felt. No time for thinking 'He doesn't mean it', 'We're both tired', 'He's getting too big for this'. I grabbed my 10-year-old and slapped him hard. With a bellow of rage he grabbed my hair and punched me in the head. I reeled back to see him coming for me again, his face twisted, his fists in the boxing stance he'd learnt at the club and shown me so proudly.

He attacked me viciously. He punched me in the head and breasts, karate-kicked me, pulled out handfuls of hair. At 10 he was strong enough to do serious damage, but I won that night. I fought him off. I went for a belt and, rightly or wrongly, used it. That's what happened to children of my generation when we did something terrible.

I sat up late that night, long after he'd sobbed himself to sleep. I couldn't cry. I just sat, pressing ice to my throbbing face, hardly able to breathe. Tom's father had been a violent man, every now and again. It wasn't the first time I'd sat like this, too shocked to cry. Like father, like son . . . my mind reeled.

Next morning Tom woke early and came and clung to me and cried and said how sorry he was. I cried, too, and said it must never happen again. It did, of course. I never hit him again but it happened and kept on happening.

Tom is away at school now - a nice, co-ed boarding school. Not a special school for disturbed children, because I never told anyone. I felt it would be disloyal. And believe me, the shame of owning up to a violent partner is nothing compared to admitting your own son beats you up. You feel it must be your fault.

I was smacked as a child. Not a lot, but I was. I never smacked Tom all that much, but now I regret ever having hit him at all. There were certainly times when I hit him for nothing, because I was exhausted and he was there. It gets written into family behaviour.

The first time Tom hit me I said: 'You must never, ever hit me, it's a terrible thing to do.' Through his tears he said: 'But you hit me]' I couldn't answer that accusation then, and I can't now.