Media playback is unsupported on your device Media caption Anaesthetists by day, inventors by night

Archimedes did it in the bath, Tesla with a walking stick and the father of the sticky note had his flash of inspiration while singing in church - or so legend has it.

Yet today we expect new inventions to be born in anonymous laboratories after the submission of several grant proposals.

But the age of the home-grown inventor may not be over.

David Williams and John Dingley are consultant anaesthetists at Morriston Hospital in Swansea. Their moment of genius came in their garages while tinkering with glue-guns and car-body filler.

Inspired by Trevor Baylis's wind-up radio, they wondered "almost jokingly" whether it might be possible to make something similarly economical and easy-to-use in the medical world.

Having the good idea is the easy part. Making it into a reality required an almost obsessive degree of dedication Dr David Willaims, Inventor and consultant anaesthetist

And having worked in remote settings, Dr Williams was aware of how crucial equipment that does not require a constant power source could be. In Zambia he had noticed entire operating theatres remaining unused because of a lack of replacement light bulbs or a reliable mains power supply.

So the doctors set themselves the challenge of inventing essential kit for the doctor's bag on a budget.

And after a week spent attacking conventional medical equipment with power tools, they had the first prototype of a device which has the potential to save lives.

The ShakerScope is a light source which can be quickly adapted to look in people's eyes, ears and throats. But unlike regular devices it does not need batteries.

Image caption The device was invaluable while working in Haiti, Dr Williams says.

Dr Patrick Finlay, of the Institution of Mechanical Engineers said: "According to the World Health Organisation, 95% of medical devices fail to work in developing countries. Often designers in the West don't understand the conditions elsewhere.

"This type of invention is very important. With these scopes you would normally need three different instruments for each examination, each one requiring batteries. For low income countries this is a joke. "

'Shaken and stored'

At the core of the ShakerScope is a powerful moveable magnet, surrounded by a coil of wire.

As noted by Michael Faraday in 1831, as the magnet moves over the wire the magnetic field induces an electric current in the coil. And shaking the ShakerScope for 30 seconds produces enough current to light the device for three minutes.

"That might not sound like long but it is more than enough time for most ear or eye examinations or to insert tracheal tubes," Dr Williams said.

Once the scope is shaken the charge can be stored for many weeks. And instead of using a conventional light bulb, it uses a light emitting diode which can last up to 10,000 hours.

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The team has designed changeable heads allowing it be converted into a number of devices.

One of its most promising uses so far has been as a laryngoscope - an instrument which lights-up the back of the mouth allowing anaesthetists to insert breathing tubes when people are unable to breathe for themselves.

It has already been tested in military hospitals in Afghanistan, in Uganda and after the earthquake in Haiti in 2010.

Image caption Different attachments will allow doctors to look in eyes, ears and the throat

"In Haiti we saw a lady with a neck injury who urgently needed a tracheal tube to help stabilise her. There were no other functioning laryngoscopes close by and the ShakerScope worked well despite the difficult case," said Dr Williams.

'Home made'

According to Dr Williams the project has been a series of steep learning curves.

"Having the good idea is the easy part. Making it into a reality required an almost obsessive degree of dedication," he said.

In the early days the doctors tried to do as much as possible from home - from teaching themselves microelectronics to perfecting their computer-aided design skills.

Luckily for Dr Williams, his wife is a sculptor who works on large pieces of metal.

He has been known to borrow her workshop, saws and glue-gun on many occasions. But he says he learned very early on that the kitchen may not be the best place to melt plastics.

Dr Jerry Nolan, a consultant anaesthetist at Bath Royal United NHS Trust, who was not involved in the research said: "The ShakerScope has the potential to be invaluable in remote locations.

"That they have taught themselves the skills to get a final version near to market is even more remarkable and surely disproves the adage doctors make poor businessmen."

The device is one of many frugal, home-grown devices recently showcased at the Institution of Mechanical Engineers in the UK.

Having made several fully-functioning versions tested across the world, the doctors say they recently reached the limit of their technical abilities, and passed on further manufacturing and design to a larger company.

But these anaesthetists have returned to their sheds and have many other possible irons in the fire.