It had not occurred to me before I tried it, that beating and kicking nine-tenths out of a body-shaped punch bag would not only be extremely satisfying but strangely exhilarating. It turned out to be both. My first attempts had been quite feeble - more of a push than a punch - but once it had been pointed out that the punch bag was not alive and could not feel anything, I started to give it the sort of hard, walloping kicks that would have impressed the likes of Bruce Willis.
This was not an exercise in gratuitous violence, however, but a self-defence class. The idea was to get you practised at hitting hard, because most people (especially women) are rather ineffectual hitters. Better not to be any kind of hitter, I hear you mutter, and of course you are right.
But if you are being physically assaulted and there is no possibility of negotiating your way out, your best bet,apparently, is to deliver one almighty, well-aimed kick or blow that will hurt your assailant enough to give you time to get away. Half-hearted hits are no good, and may make things worse, so you have to do it properly, or not at all.
The advice comes from self-defence expert Tony Lloyd, whose organisation, Fighting Fit, runs courses in streetself-defence (as well as kick-boxing, kung fu and karate) at the David Lloyd (no relation) sports club in Wimbledon. But, although Mr Lloyd is a black belt in almost anything you care to name, he is no advocate of automatically responding to violence with violence.
"We always say that the first rule of self-defence is to run away, or, if that's not on, to try and talk your way out of danger," he says. "Physical self-defence techniques are for when you're trapped - when someone has already made the first move and you're in no doubt that they intend to hurt you."
Fortunately, the average, law-abiding person's chances of becoming the victim of violent crime are quite low. Most street violence is inflicted on young men aged 15 to 22 and alcohol usually plays a part.
Nevertheless, the number of muggings, rapes and violent assaults in the metropolitan area of London has risen by more than 25 per cent in the past three years. Women are more at risk from people they know than from strangers, and older people, ironically, are more likely to be victims inside than outside their own homes.
According to Mr Lloyd, it is particularly important to know what to do if you are threatened with attack in your home, because the likelihood is that no one will hear you if you shout. But even he admits that, to be any use, self-defence techniques have to be practised constantly. For that reason, he prefers to incorporate them into keep-fit and martial arts classes, rather than teach them separately.
"Fitness, physical confidence and self-defence are all part of the same thing. You need to be fit to run away from danger, and you're much less likely to become a victim if you look physically confident. People can sense confidence in others, inthe same way that dogs can sense fear."
Considering I only dropped in for one session, I learned asurprising amount - how to deal with someone who has you in a stranglehold or has taken hold of your wrist; how to force an assailant to the floor; howto disarm someone with aknife and how to turn an attempt to strike you to your own advantage.
In a role-playing situation, the techniques certainly worked and did not require physical strength. But to be able to use them in a moment of crisis, they would have to become second nature.
As no one ever gets hurt in Tony Lloyd's class, the speed ball and punch bag are there so you can get used to the feel of really hitting something soft. You are shown how to use elbows, feet, hands and knees as effective weapons and which part of an assailant's body to aim for in differing circumstances.
Some of the advice was refreshingly non-technical - for example, if someone is being a nuisance on the Tube, it is usually enough to stamp hard on their foot.
Mike Smith, a 28-year-old south London maths teacher who has been doing ju-jitsu since he was a teenager, is convinced that martial arts give people a demeanour that others respect. "I'd call it a 'presence'," he explains. "You don't look like a victim, so you're unlikely to become one." Ju-jitsu, which he teaches at the Budokwai Club in Fulham, west London, is particularly relevant to self-defence, he says, because it is situation-based. He's never had to use it to defend himself, but did once get a friend, who had been surrounded by a group of thugs, out of trouble. "I haven't ever used it in a school context," he adds, "but if two kids were fighting I'd know how to take one out of the equation safely. The point about martial arts is that it teaches you how to avoid a fight."
Thirty-year-old office worker John Pierson says kick-boxing and self-defence have made him a different person. "I used to be a bit of a waste of space," he admits. "My life was beer and television and I didn't even walk to the shops. Fighting Fit has given me confidence, not just walking down the street, but at work, too."
Julie Coleman, 29, was bored with aerobics and wanted to do something different. "My main reason was fitness but I also liked the idea of being able to look after myself."
If it came to it, would she be able to? "I don't know, but I'm fitter and stronger and that would definitely work in my favour."
Contact Tony Lloyd at Fighting Fit on 0181 874 1274. The Budokwai Judo and Karate Club is at 4 Gilston Road, London SW10. Tel: 0171 370 1000