Leeds nostalgia: Britain’s post-war plan to blow an island out of the water to use up its left-over munitions... but did it backfire?

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One of the problems the Allies had at the end of the Second World War was they had a lot of munitions and not much to do with them.

This led to some creative ideas, one of which was turned into reality seventy years ago today, after Britain created the world’s largest non-nuclear explosion by trying to blow up an entire island.

The islands in question was part of the strategic archipelago Heligoland, dubbed Germany’s ‘Gibraltar’, a small cluster of islands some 46km off the German coast.

Seven thousand tons of explosives were used including 4,000 torpedo warheads, 9,000 sea mines and over 51,000 grenades.

The whole lot was detonated on the third pip of the BBC’s one o’clock time signal. By 1.06pm, the cloud from the explosion was 8,000ft high, a mile long and a mile wide.

A BBC observer, travelling overhead in a plane, said: “The whole of Heligoland jumped into the air. It was the biggest firework display I have seen in my life. It went up with a cloud of masonry like skyscrapers and the sea for half a mile around was covered in a white cloud of splashes as masonry fell. Immediately afterward two enormous clouds appeared, like tremendous mushrooms.”

One goal was to measure the vibrations created by the explosion and the first tremors were indeed detected at Kew some three minutes after the explosion.

Meanwhile, HMS Dunkirk, which was nine miles away, heard the blast 45 seconds after detonation.

Britain had intended to blow the island up completely but in the end they only succeeded in creating a giant crater, which today is a tourist attraction.

Still, the German fortresses, once considered impregnable, were completely and utterly obliterated.