`The holder of this card is schooled to the highest level in the use of sarcasm, badinage and ironic exaggeration'

Everybody remembers the teacher at school who loved practical jokes, the big man (it was always a man) who thought it was really hilarious to send the thickest kid in the class to the shops for a tin of elbow grease. Nobody remembers them with affection - the one from my primary school swam unbidden into my memory when I was reading recently about a famous film star and noticed that he was described - as if this were a good thing - as "a great practical joker".

I hate practical jokes. When an actor is described as "a great practical joker", hilarious stories are rolled out about him poking people's eyes out to the merriment of all concerned, especially the eye pokee who finds it the most amusing of all. Crap of course. A "great practical joker" is another term for a power-crazed egomaniac. You can bet that they can set fire to the crew's trousers, or bring a herd of cows on to the film set, but let any subordinate try anything like that and they'd find themselves the subject of the highly impractical joke of being fired. Practical jokes are just another form of tyranny.

Adolf Hitler originally said that he'd invaded Poland "just for a laugh" and that the Allies were a pack of humourless gits for not getting the joke and so he was going to invade France and the Low Countries as well.

Another form of power trip on a film set can be "corpsing". This is supposedly involuntary laughter and is again an activity that's strictly confined to the star. The star finds what he is doing or saying so hilarious that he cannot help himself and starts laughing and can't stop. This usually happens when anybody else in the scene with him has performed better than him - laughing like this means they have to do the scene again and again until the star gets it just right.

The finest example of this is Peter Sellers. You can always see clips of him on It'll Be Alright on the Night breaking into giggles during the shooting of various Pink Panther films. On the surface this looks like "all mates together having fun on the film set", but if you look closer at the faces of the actors around Sellers, you can see their expressions are a rictus of annoyance and embarrassment - they are not having a good time, they are watching a star showing off his power by saying: "I can hold up filming whenever I want by pretending to giggle like an idiot, but don't any of you try it because I'm the boss of this picture."

Any form of practical jokery is just another form of bullying and should be stomped out by a special police force dedicated to this task. Following in the shoes of the Serious Crimes Squad, they could be called the Silly Crimes Squad. Of course, you might think that I, as a professional laughter- maker, am always going to be prejudiced against any form of humour that people can do to each other without the intercession of a paid humorist, but this is as far from the truth as it's possible to get.

We comedians, in fact, are loath to use our gift in public; it is a weapon we prefer to keep sheathed except in the controlled environment of a professional engagement. Rather like karate experts who, as I'm sure you know, are required to carry a laminated card with them at all times, which has to be shown to anybody who tries to get into a fight with them outside the gym and which states, "The holder of this card is a karate expert and is therefore trained to inflict serious damage on an opponent, you should be aware of this fact before engaging in any physical contact as they cannot subsequently be held responsible in law for any medical injury which could result. Signed Chief Commissioner, Metropolitan Police."

Similarly, those of us whose paid vocation is the giving of laughter are required to carry an almost identical laminated card, which states: "The holder of this card is a trained humorist and is therefore schooled to the highest level in the use of sarcasm, repartee, badinage and ironic exaggeration. If you are inclined to get into an argument, escalating flight of fancy or battle of wits with the aforementioned holder of this card, the law will not hold him or her responsible for any loss of face, feelings of lowered self-esteem or experience of embarrassment which may be suffered. (However, as most comics are lefty physical wimps and are unlikely to be trained karate experts, you could try giving them a smack in the mouth when they start in with their smart-arse remarks.) Signed, the Home Secretary."