Some of the best inventions are the ones with that "why didn't I think of that?" (WDITOT) factor. How the Aztecs, who built their giant pyramids without the benefit of wheels, must have smacked their foreheads when they first caught sight of Spanish carts.

How a Roman, sweating over the answer to MCLXXXVII divided by MCCLXVII, might have wished the Arabs would hurry up and introduce 0. (On the other hand, looming millennium celebrations, heralding the arrival of the maximum number of zeros on the calendar, might persuade any ancient Roman still around to stick with capital letters.)

Corkscrews, hot water bottles, and many items of stationery such as paperclips, bubble wrap, see-through sleeves and Post-it notes - all have that satisfying, simple ingeniousness. Those milk cartons with annoying plastic pourers do not.

Trevor Baylis is a man who understands the virtues of low-tech. He is the inventor and maker of the BayGen Freeplay wind-up radio, which runs not on mains or batteries, but on clockwork. You turn the handle 60 times, or for 25 seconds, and it will give you 25 minutes of playing time.

An engineer by training, 60-year-old Baylis has worked for much of his life as a circus performer and stunt man. The result is a preoccupation with disability. "A lot of my stuntman friends came to a grimy end," he explains.

In 1984 Baylis founded a company called Orange Aids which made devices for the disabled such as one-handed can openers and foot-operated scissors. The company was struggling when, in 1993, Baylis saw a TV report on Aids in Africa. It said that the lack of communications in remote areas was preventing the spread of health education to help contain the epidemic. Baylis thought of the old-fashioned gramaphone, powered by elbow-grease. He made a radio in which a spring linked to a gear box worked a dynamo which powered the radio.

There's a green, ethical and practical invention for you, with oodles of WDITOT appeal. But when Baylis took the idea to electronics companies such as Phillips and Marconi, they could not see it. Nor could the Design Council. "If you want to be talked down to, go to the Design Council," advises Baylis.

Reluctant to expose his idea to the whole world, but desperate, Baylis asked the producers of TV's Tomorrow's World to feature the radio. It just so happened that, on a visit to England, the mergers and acquisitions director of a firm of chartered accountants in Cape Town saw the programme and offered to finance the idea.