"The radio is not the end of the story but the start," says Chris Staines, chief executive of BayGen, based in London, which makes the radios. "We want somebody with a lot of money and technical resources to take this to an international level. In developed countries, the market potential and possibilities for everyday small portable items are huge."
The radios, which were featured on the BBC's science programme QED last week, can run for an hour from two minutes' winding. They are the brainchild of Trevor Baylis, who saw the potential usefulness of a non-electric power source for the Third World. About 20,000 per month will be made in South Africa for sale there.
But in Britain they have also sparked enormous interest. Harrods, which will be selling them from October, says that hundreds of people have rung up to order them since the programme was shown. "I suppose there must have been another product that created this response, but I can't think of what," said a spokeswoman. "And the profile of the people contacting us is different from those who usually buy radios, who are older. These are young, and interested in it from a green perspective."
Harrods has been allocated thousands of the radios for sale by the end of the year. But now Mr Staines is looking further ahead. "Trevor had three years of frustration in trying to get to this stage," he says. "The initial investment to get to here was about pounds 250,000 in the UK and pounds 600,000 in Africa. Now we need about 10 times that to step up so that there's a whole family of products."
BayGen's European managing director, Barney West, reports a flood of inquiries from British and foreign companies eager to exploit the technology. The clockwork systems work by slowly and constantly releasing energy stored in a spring and converting it into electricity to power equipment. In the radio, the spring assembly is about as big as a fist. "But we could already make it smaller and lighter, though not yet miniaturised," says Mr West.
BayGen has already spoken to Battelle, a US company, about the possibility of making a miniature version of the spring mechanism and says it has been in talks with toy manufacturers for more than nine months.
A manufacturer with sufficient technical resources might be able to crack any problems that emerge, reckons Mr Staines. "This could work for anything that's portable, doesn't have large power requirements and uses batteries," he says. "A Sony or a Samsung that makes a range of electrical products would be an ideal sort of partner." But he declines to name companies that have so far got in touch. "It could even work for a battery company; we're never going to make a serious dent in their sales worldwide."
Products such as hand-held clockwork Gameboys would be ideal, he says: "Maybe one day sales of those would outstrip that of radios 10 to one".