The factory was the newly-built BayGen plant in Cape Town whose workforce,many of them disabled (the company, in line with Baylis's wishes, has a policy of recruiting people with special needs), had just started mass-producing Baylis's award-winning clockwork radio. After the factory visit the inventor was taken to meet Nelson Mandela. "He told me it was a great achievement. Can you imagine how far that was from the discouragement I had met at the beginning?"
Now the clockwork radio has spawned the clockwork computer. At the Commonwealth Ministers' Council in Botswana last year, Baylis linked an Apple notebook computer to one of his spring motor generators, and the computer ran for 15 minutes on one winding. The idea is being looked at by BayGen engineers and wind-up laptops could be in the shops by the end of the year.
It's all a long way from the days when he was portrayed in some quarters as a nutty professor. As he says: "Now, if I talked about a clockwork sausage, people would listen."
The journey that led Trevor Baylis, 60, to Nelson Mandela's study (and to wealth and an OBE, to say nothing of a spot on This Is Your Life) started in a swimming pool. After spending his National Service in the Intelligence Corps, in the Fifties he became an international swimmer and earned a living as an exhibition swimmer and diver. He then set up a business selling swimming pools to schools. His urge to invent has run parallel to this career - in the Eighties he made a can opener that can be operated with one hand, one of many devices he has designed for people with disabilities.
Then, three years ago, Baylis saw a TV programme about the role of radios in getting information about Aids to remote parts in Africa. The problem, the programme explained, was that batteries were too expensive. Remembering his old wind-up gramophone, Baylis wondered whether he could make a wind-up radio. That evening he made the prototype of what was to become the Freeplay radio, sales of which have now hit 300,000.
The road ahead, though, was not straight. Two letters from early 1992 are typical of initial reactions. One is from the Design Council, which liked the idea but doubted its commercial viability. "The major customers are Third World countries which, with severe debts, would not be able to pay for this device," it says.
Another letter from 1992, pinned up in the toilet of Baylis's studio on Eel Pie Island, Twickenham, is a reply to an appeal for information about spring engines. "Neither of us considers a spring engine to be a practicable means for your purposes,'' writes an unhelpful respondent. The letter goes on to explain that 10 minutes' running time would need a clockwork motor weighing a hundredweight. (The Freeplay radio weighs no more than any other portable model, and runs for nearly an hour on one winding.)
It was the radio's appearance on Tomorrow's World in 1994 which brought it to the attention of people who could see the possibilities. Lynda Chalker, then minister for overseas development, allocated funds, and City banker Christopher Staines became a key player in making the radio a commercial proposition and setting up BayGen with South African entrepreneur Rory Stear.
Trevor Baylis's experience of trying to get his ideas taken seriously and to turn his pencil sketches into real, manufactured products led him to his latest project. He is lobbying for the creation of a Royal Academy of Invention - an irreproachable professional organisation, with royal patronage if possible, to be overseen by respected inventors and others who understand the issues - that would advise inventors, examine their ideas and guide them through the minefield of patenting.
His plans are advanced, and he is vigorously lobbying anyone who will listen. He has already been promised a room for planning meetings at the Institution of Mechanical Engineers. And his idea seems to have struck a chord with the Government. A spokesman for Chris Smith, the Culture Secretary, says: "We welcome this initiative, which is totally in line with the Government 's ideas on developing a more intelligent and informed view on protecting and developing intellectual property. We are particularly interested in ensuring that the rights, and the resulting business and employment, remain in the UK."
Such ambition seems unlikely when you visit his "studio" on Eel Pie Island, a workshop filled with tools, discarded components, a well-used lathe, lots of bits of wire, an eager dog, and an enthusiastic, engaging and at times scandalously funny man in jeans with one of the loudest laughs you have ever heard. But Baylis is as passionate about his plans for the academy as he is about any of his inventions.
His main concern is with the way that inventors can be fleeced; naivety can be expensive. The crux of the problem, Baylis says, lies in the gap between the "Eureka!" moment and the beginning of commercial production. While the inventor is looking for a manufacturer, it is crucial that he or she is protected as the owner of the idea - a process which is both expensive and difficult. Inventor Branko Babic, who has worked with Baylis, and has suffered unpaid royalties for his own projects, says: "The patenting system is cumbersome, clumsy and most involved, and your salary goes nowhere in a court of law. "
A wrong decision, or meeting the wrong person, may mean an idea is lost, or the inventor is shut out of the profits. "There are people who advertise for ideas - you send them your idea, and money, and they take the money and do nothing," Baylis says.
Another problem is the behaviour of firms which look at ideas, reject them - "We're already working on something like this" - and then plagiarise them. "The more valuable a thing is, the more attractive it becomes to the odds and sods who will rip you off," Baylis says.
He also has doubts about some of the design and technology competitions and exhibitions that seek presentations from young people, feeling that ideas which should be protected may end up on public view. "These competitions should be held initially in camera. Young people could lose all opportunities to profit from their idea, or to be acknowledged as inventors.
"Through the education system we have to teach them about intellectual property and protect them from exploitation."
He believes, too, that more attention should be paid in schools both to the image and role of the inventor and to the encouragement of creative ideas.
"We must make people aware that it's healthy for youngsters to experience the enjoyment of seeing things light up and change shape. It's essential that children are encouraged from a very young age to indulge in this type of creative activity."