An engineer built a “horrendously dangerous” electro-magnetic cannon as part of an experiment to discover whether trillions of mirrors could be sent into space to protect the Earth from global warming.

Tod Todeschini assembled the four-metre long gun in the back garden of his quiet Standlake home to test an American professor’s radical theory that a 100,000 square mile sun shade could be created in space and used to deflect sun rays.

The aim would be to halt climate change.

Mr Todeschini, usually known for making medieval weapons, believed the idea was “do-able”.

The sunshade concept, developed by astronomer Prof Roger Angel, is based on the idea of creating a one kilometre gun powered by hefty electro magnets.

Prof Angel believed a bigger gun could be built to deliver 800,000 mirrors into space every five minutes.

The mirrors would link up in space to deflect the sun’s rays.

Mr Todeschini was commissioned to produce a scaled down, but highly-powered prototype of the weapon, which wielded enough power to boil 44,000 kettles.

It also packed enough punch to shoot an object from zero to 100 mph over a space of just two inches.

It took Mr Todeschini five weeks to construct the weapon, which will be shown in action in a TV documentary at the weekend.

However, its devastating power meant it had to be decommissioned for safety reasons as soon as filming finished.

The weapon, which weighed half a tonne, was fired about 20 times over three days of filming in December 2007.

After the test-firing on a farm in Besselsleigh, it was shipped off to the United States to fire mirrors in a desert next to Lost Dutchman’s Mountain, in Phoenix, Arizona.

Mr Todeschini admitted he did not enjoy taking his life in his hands when working with the cannon.

He said: “The gun was horrendously dangerous. This was the first gun I’d ever built.

“I knew I could put it together safely but at the end of it all I didn’t know what I was going to get.

“It was immensely dangerous. I was attempting to build a gun to produce 1,500 g of force but it ended up creating about 10,000 g and we had to turn the power down.

“The main danger was electrocution.

“If you were working with normal levels of electricity you could get a shock and be fine, but if you got a shock off this you would be dead – no question.”

It was a case of being transported from the Middle Ages to the space age for Mr Todeschini, whose main job is making medieval crossbows, swords and axes.However, the TV engineer, who has worked on Channel Four show Scrapheap Challenge, is used to building unusual contraptions in short time frames.

Mr Todeschini said: “I think putting the mirrors in space is do-able if enough money is thrown at it.

“The guns needed to fire the mirrors would be much smaller than the Large Hadron Collider so it shows that these kind of projects are possible.”

Viewers will be able to see Mr Todeschini’s gun in action when Ways to Save the Planet airs on the Discovery Channel on Sunday at 7pm.

cwalker@oxfordmail.co.uk