The deadliest man-made explosion before the atom bomb was so loud the Prime Minister heard it in London 140 miles away.
British military engineers detonated a million pounds of explosives under German lines at 3.17am on June 7 1917, hastening the end of the Great War.
Major General Charles Harington told war correspondents witnessing the secret operation: “Gentlemen, I do not know whether we shall change history tomorrow, but we shall certainly alter the geography.”
Ten thousand Germans are believed to have died when mines exploded near the Belgian villages of Messines.
The few to survive gathered like wraiths on the rim of the crater, deafened and too shocked to fight.
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Artillery officer Ralph Hamilton saw the blast from 15,000 yards away. He said: “There was a double shock that shook the earth like a gigantic earthquake. I was nearly flung off my feet.
“Then an immense wall of fire that seemed to go half way up to heaven. The whole country was lit with a red light like in a photographic dark room.
“At the same moment all the guns spoke and the battle began on this part of the line. The noise surpasses even the Somme: terrific, magnificent, frightening.” The mines left a crater 145ft deep and 380ft wide.
Allied troops went on to seize the vital Messines Ridge, in a battle described as one of the most unalloyed victories of the First World War.
Tunnellers, mostly civilians, including the legendary Manchester moles – sewer workers – had toiled for two years to create a subterranean earth shock in advance of an attack on the Messines Ridge by 80,000 Allied troops.
Their heroic exploits are celebrated in a new film out on Friday, The War Below, starring Sam Hazeldine.
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He plays William Hackett who, with fellow workers, built the Edwardian sewage tunnels under Manchester and were desperately needed at the Front.
They were unmilitary in bearing: short, stocky, and – like the navvies who built the canals – no respecters of authority. A report said: “They couldn’t march, drill or salute, and were more likely to call an officer mate than sir.”
The Manchester Moles formed the initial deployment of 170 (Tunnelling) Company, Royal Engineers, and reputedly could dig four times faster than their German opponents who were tunnelling towards the British lines.
The 19 mines dug up to 100ft deep below the German lines at Messines were set off at short intervals to destroy enemy morale.
It was the idea of eccentric, military brainstormer, Major John Norton-Griffiths, the MP for Wednesbury, in the West Midlands, known as Hellfire Jack.
He reputedly toured the trenches in a Rolls-Royce loaded with cases of port. But he was far from a crank.
His biographer Tony Bridgland said: “He was an entrepreneur, a go-getter – not a glory leader, but the type of man who didn’t sit on his hands and liked to get things done.”
Alamy Stock Photo)
He brought to warfare the skills of workmen for his engineering company Griffiths & Co. The heavy clay of Flanders was similar to Manchester’s geology, and was perfectly suited to the tunnellers’ technique of “clay kicking”.
Instead of hand-held picks, they sat up against a wooden support and drove a small blade into the clay face, a noiseless operation that would not be heard above ground or by German tunnellers.
Norton-Griffiths’ plan nearly failed. He had tried to convince War Secretary Lord Kitchener his “handful of moles,” as he described his Manchester men, could beat the Germans at their own game.
Alamy Stock Photo)
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But his letter was filed under “M” and forgotten until German underground attacks became more deadly and Kitchener, a family friend, changed his mind.
According to Hellfire Jack’s granddaughter, Norton-Griffiths demonstrated the clay-kicking method in the politician’s office.
Kitchener – the man on every poster urging Your Country Needs You – called for 10,000 moles. There weren’t as many as that in the whole country.
Tunnelling, like heavy construction work today, was the preserve of highly skilled men who moved from job to job.
Eighteen Manchester men who passed the Army medical were enlisted as sappers, working with soldiers from other battalions who knew mining.
Military historian Jeremy Banning said: “These men had changed from civilian to military in a matter of days.”
More were found in the slate, mineral and coal mines of Britain, and some came from the Empire.
The tunnellers’ skills earned them six shillings a day, while a soldier in the trenches got one shilling and threepence.
On top of the dangers of the Front, tunnellers risked carbon monoxide poisoning and, like coal miners, took caged canaries with them to warn of the colourless, odourless gas.
Only 12 of the original Manchester 18 survived and five were awarded the Silver War Badge for those honourably discharged due to wounds or sickness.
Mr Banning said: “Sewer men that at home might often have been looked down upon as grubby, rough and ready industrial types were the most prized troops on the Western Front.”
Just this week the National Miners’ Memorial for all those who worked in the mining industry and served or died for their country was unveiled at the National Memorial Arboretum at Alrewas, Staffs.