The fine art of making it up as you go along has been around for a long time. Originally used as a technique for teaching actors to act, and to develop new script ideas, it was a young actor named Keith Johnstone who first brought it to public attention.
His book Impro, first published in 1979, remains the seminal work in the field, and the organisation he helped to found, TheatreSports, is the main worldwide network of performers. But it took television exposure to bring impro to the attention of the great British public.
Channel 4's Whose Line is it Anyway? (above right) was first broadcast in 1988, and suddenly everyone wanted to have a go. As well as making stars of Mike McShane, Tony Slattery, Josie Lawrence, Paul Merton and Clive Anderson, the programme also provoked a massive increase in interest in impro as both a spectator and participation sport.
The transition from payer to player couldn't be easier. There are dozens of workshops all over the country offering basic introductions to the skills behind good impro and taking you right up to performance level. Whether you are an actor looking to expand your repertoire, a writer hoping to free up your creative processes, or just someone who enjoys larking around, these courses have a lot to offer.
You will learn how to "make offers" - suggestions for developing the scene. And equally important, you will learn not to "block offers" from others.
For example, if you begin a scene by miming painting a wall, and someone comes on and says, "Haven't you finished grooming that horse yet, corporal?" - that is an offer, and responding with, "It isn't a horse, it's a wall and don't speak to me like that, I'm your father," would be blocking. It might get you a laugh (in which case it is also an example of gagging) but it stalls the scene, destroys the illusion of truth and leaves you nowhere to go.
On the other hand, saying, "No sir, I don't seem to be able to get the paint out of its coat," would be "accepting" and "building" and adding something new.
It is developing the flexibility to deal with these constant challenges to your prior visualisation of the scene that makes impro fun. And it is from seeing you struggle that the audience derives its chief pleasure.
You will learn about "status' (eg "corporal" and "sir"), "raising the stakes" ("But this is The Queen's horse for the Trooping of the Colour"), and the other hidden mechanics of good impro.
Don't worry - you won't be asked to improvise a sequel to War and Peace at your first workshop. But you might be astonished at how quickly you learn the skills even when you're starting from scratch.
You may also be surprised at how impro can enliven your thought processes in everyday life. Still, don't be surprised if your father's response to enquiries about the Queen's horse are met with a firm "block" - and a demand that you finish painting the wall.
TheatreSports UK (Natalie Haverstock, 0181-450 8830).
Courses are also run by Spontaneous Combustion (Stella Duffy, 0181-346 7487).
Keith Johnstone's 'Impro' is published by Methuen, price pounds 7.99.
The seventh series of 'Whose Line is it Anyway?' begins Friday 10.30pm C4.