The nine shrapnel bombs were among the most sophisticated devices of their kind ever found in Britain.

The cache of explosives built by Jonathan Wilkes contained plastic water bottlers crammed full of steel nuts.

Created to explode like hand grenades, when detonated these nuts would have flown from the device with lethal force -- capable of killing anyone within 15-feet.

Some were also booby-trapped to detonate if they were picked-up and the Army had to be called in to make them safe.

Explosives expert Kim Simpson, senior case officer at the Forensic Explosives Laboratory in Kent, said that the "very sophisticated" cache was unique in her experience.

She said that three of the bombs found at Freeland were triggered by two radio control receivers -- one to ready the bomb for firing and a second to set it off.

"I have never come across any radio controlled devices constructed in this way before," she said.

The design of the weapons meant that the bombs could be left for days in a "dormant" state without the batteries inside becoming drained.

She added that she had not seen anything like the time delay devices built by Wilkes, a computer software engineer, on five of the bombs which worked using alarm clocks and were marked with labels saying one hour, three hours, four hours and seven hours.

The device would have to have been made by someone with a knowledge of radio control, she said.

Mrs Simpson added that it was "possible" someone playing with radio controlled models or broadcasting on CB radio in the area could set them off.

Police believe the bomb found at Syreford, Gloucestershire, was a test device that failed to explode and was too dangerous for the bomber to move.

Det Supt John Donlon, of Thames Valley Police, said: "It was unusual to find devices so sophisticated, which had been put together with such finesse and intelligence."

Wilkes, explaining how he made the devices, said: "In terms of the explosive section, that really was basic physics and thinking about it. In terms of the electronics of the two types, the alarm clock one was just basically things you know. I don't know how I know them.

"The radio control types, they evolved from a fairly simple idea into something quite complex."