Trevor Baylis' wind-up radios could work anywhere.
They were sold in the UK, but we weren't the intended market.
What made them important was that they were designed for a Third-World application.
They were aimed at Africa and places where mains electric power and access to batteries was a problem.
The original one had a clockwork-like mechanism with a very ingenious double-spiral spring. It wound off one pulley onto another and would run for relatively short periods of time - about 15 minutes.
Later versions lasted longer and were powered by rechargeable batteries. They were charged up with a crankable dynamo or could be plugged into the mains or solar energy panels, if available.
Nelson Mandela would say fine things about them, and they won Trevor Baylis various prizes.
But while the Baygens certainly sold and were used, their biggest impact was probably that they had been made by a First World engineer who cared about the Third World.
There are now all sorts of inventions aimed at the developing world and it's a relatively common thing for young engineers to dedicate themselves to, but that didn't always used to be the case.
I think Trevor Baylis deserves considerable credit for having kicked that off and for having served as an inspiration to many other young engineers and inventors.