The Lost Mines of Messines: The Blast 'Heard in London' That Wasn't, and the Six Bombs Still Under Belgium

The story is told with total confidence. Nineteen mines under Messines Ridge, the loudest man-made sound in history, heard in Downing Street, ten thousand Germans gone in a second, the biggest explosion before Hiroshima.

So we pulled the records.

The tunnelling is real, and it is astonishing. For up to two years, British and dominion tunnelling companies dug through the Flanders blue clay in secret, laying some twenty-five mines, around a million pounds of explosive, under the German positions. At ten past three on 7 June 1917, nineteen of them fired along six miles of front. A geologist in Lille thought it was an earthquake. Seismographs near Utrecht and on the Isle of Wight, about 180 miles away, recorded the shock.

Then the legend starts inflating. 'Heard in London' traces to The Times of 8 June, which reported that Lloyd George heard the blast at Walton Heath in Surrey, 140 miles away. The same item noted that people near Downing Street heard what they judged to be heavy guns. Nature repeated the story, then printed a correction a fortnight later after hearing from Royal Engineer officers who had watched the mines go up. One, a mile away, called the sound 'not so very great'. Another, at eight miles, saw the flash, waited, and heard 'a slight phit'. For the first time in the war, the mines were the signal for the artillery: more than two thousand guns opened fire in the same second. The historian Simon Jones, who traced the whole story through the archives, concludes that what England more likely heard was the barrage. Gunfire from Flanders was already audible in London that week.

The body count inflated the same way. The 10,000 figure appears to enter print in a 1998 popular history. The German Official History lists 10,000 missing over a 21 day window, and British sources counted 7,200 of those men as prisoners. Major Ralph Stokes, a mining engineer on the staff of the Inspector of Mines, walked the craters on the day of the attack and recorded ten to twenty dead at each of the southern mines he examined. Scaled honestly, the mines themselves likely killed fewer than five hundred men. The real weapon was shock. The ridge fell by mid-morning.

And the superlative? Halifax harbour, six months later, roughly six times the energy, by accident. Messines keeps a narrower crown: the biggest planned explosion in warfare to that date.

Here is the part the legend never mentions, and it is better than the legend. Six mines never fired. On 17 June 1955, lightning struck a power pylon that had been built above one of them, the current found the detonators sixty-five feet down, and a Belgian field erupted. The casualties, per the records: cows, the pylon, a stretch of road. The other five charges are still in the ground. One of them, 50,000 pounds of ammonal, sits beneath a working farm.

Verdict: MOSTLY BS. The tunnels, the scale and the shock are real and primary-sourced. The London sound, the ten thousand dead and the Hiroshima comparison are folklore the record does not support.