'It's a perfect solo sport', says Peter Harding, one of this weekend's throwers. 'You play with the wind and against yourself. I got into boomerang throwing when I got fed up with pals cancelling squash games. A boomerang's a lot more reliable.' In fact, if you throw it the right way, you are hard pressed to lose the thing, no matter how you try.
Boomerangs are not just good sport, they are also an extraordinary form of aeroplane, dating back at least 20,000 years before the Wright brothers took to the air in The Flyer. They are not specifically Australian in origin: the earliest known boomerang - made from a mammoth's tusk - was discovered in Poland. The oldest Australian boomerang, hewn from the elbow section of the branch of a mulga tree some 10,000 years ago, was found at Wyrie Swamp, South Australia.
The flying characteristics of boomerangs are sophisticated and infinitely tuneable. You can get them to fly in tight or lazy circles. And the nice thing is that many of these characteristics are shared by cardboard boomerangs suitable for children to throw harmlessly indoors and competition boomerangs made from expensive plastics that can fly for very nearly two minutes at 90mph in circuits of 100-yards plus.
'You don't need any great strength to throw a boomerang,' says Sean Slade, a physics teacher who started making boomerangs three years ago and now runs the 100-member British Boomerang Society. 'It's all in the wrist action. Most boomerangs weigh little more than 2oz; these will happily fly in 25-yard circles at speeds of up to 70mph. Last year the world distance record was set at Shrewsbury by a Frenchman, Michel Dufayard; his boomerang flew for several yards about six feet off the ground before climbing into a 147-metre circuit. The boomerang weighed just 4oz.'
There is no definitive design of boomerang, although the double-winged wooden wonder flown by Australian aborigines for thousands of years is how most of us picture one. Today's sports models may feature three or even four wings. They come in all shapes and sizes and are made of a variety of materials. Most are designed to return in flight, but some heavy- duty boomerangs fly on a one-way ticket, aimed at flooring an animal as big as a kangaroo.
This indefinite quality is appropriate because the boomerang is a kind of Bruce-of-all-trades in the world of weapons-turned-sports-equipment. Australian aborigines have used them like we might a Swiss army penknife - for self-defence, hunting, bird-scaring at billabongs, for cooking, making fire and for digging delicious witchety grubs out of bush trees at meal times. They have also been used as clapping sticks to accompany rythmic dancing.
A debate rages among enthusiasts, however, as to what exactly constitutes a boomerang. There are purists who argue that a boomerang can only be crafted from a curved section of wood, and progressives who see nothing wrong in making a boomerang from high-grade aircraft ply or a resin-compound such as Paxolin.
Traditionalists say another word should be found for today's competition boomerangs that have as much in common in terms of form and structure with traditional boomerangs as a contemporary Formula One Ferrari does a 'Blower' Bentley. The argument will probably go round in circles for years to come.
'Boomerangs aren't used much for hunting these days,' says Peter Harding, 'and - made of modern, lightweight materials - they aren't particularly dangerous. You can go and throw them in parks quite safely when you know they will return. It's best though to find somewhere fairly deserted to crack the technique.'
'I like to restrict the span of the boomerangs I make to 10 inches,' says Sean Slade. 'Boomerangs can fly at up to 90mph and the bigger the span, the more dangerous they are. Ideally, a boomerang shoots almost vertically from the hand and in the course of its flight gradually tips on its side and loses momentum. By the time it comes back to you, it should be flying like a sycamore seed, so slowly that you can pick it out of the air with one hand.'
Traditional boomerangs can fetch thousands of pounds at auction. A one-ounce, 10-inch plastic 'learner' can be had for pounds 3, and even the smartest designs cost little more than pounds 20. No other equipment or special clothing is needed. The boomerang is making a comeback - it can hardly do anything else.
Boomerang] (an exhibition of more than 200 boomerangs from the South Australian Museum, Adelaide) until 8 August, Royal Festival Hall, The South Bank Centre, London SE1 (071-921 0600). Today and tomorrow, 1pm and 4pm demonstrations of synchronised boomerang throwing from roof of Queen Elizabeth Hall, South Bank Centre, London SE1. British Boomerang Society, 1 Berkeley Avenue, Mapperly Park, Notts NG3 5BH (0602 604992).
Suppliers: Michael Hanson, School House, Sinclairston, Ochiltree, nr Cumnock, Ayrshire (0292 590609); John Jordan, 9 Bowood Drive, Tettenhall, Wolverhampton WV6 9AW (0902 742288); The Kite Store, 69 Neal Street, London WC2H 9PJ (071-836 1666).