On 17 July 1955, a thunderstorm swept across Flanders in Belgium. Lightning struck a pylon carrying a power line and unleashed a colossal explosion underground, leaving a crater 20 metres deep and 40 metres wide. A cow was killed, the pylon was destroyed, windows in houses for miles around were shattered, but no one was injured.
The lightning had detonated a mine left deep underground from the first world war. In 1917, the British laid 19 mines packed with 454 tonnes of explosives in tunnels under the German trenches at the Messines ridge.
On 7 June 1917, the mines were detonated along a six-mile front, creating one of the largest non-nuclear explosions in history. Fire, smoke and debris blasted into the sky, obliterating the German lines and 80,000 British troops rushed in and took the ridge.
Two of the mines were deliberately left abandoned and unexploded because the Germans had moved their lines. The mines were forgotten, but decades later a power line was built across the battlefield and the pylon unwittingly placed above one of the mines.
It is thought the lightning struck electrical leads to detonators 65ft underground and set off the explosives. The location of the other abandoned mine remains unknown.
