It happened on the morning of December 6, 1917, in the Canadian port of Halifax. Nearly 2,000 people paid with their lives for a series of blunders that seem grimly predictable in retrospect. First there was the folly of loading that vastly volatile mixture on to a small and barely seaworthy boat. The Mont Blanc, just one of the many warships in the port on that wintry morning, had been given the job of transporting the stuff across the Atlantic.
But she didn't hoist the regulation red flag that would have warned others of her dangerous payload. Then she got entangled in a confusion about right of way in the channel with a bigger ship called the Imo. Just at the wrong moment, both captains ordered their engines into reverse. The Imo's bow swung to the right - and struck the Mont Blanc.
Then there were sparks.
The Mont Blanc's sailors took to the lifeboats. Their screamed warnings went unheeded as their ship drifted back towards Halifax, setting fire to one of the piers. The fire brigade arrived - and so did many curious residents.
And then there was the bang.
It levelled more than 300 acres of the town. The shock waves were felt nearly 300 miles away. Windows shattered 50 miles away. The barrel of one the ship's cannons flew three miles. The town's hospitals were overwhelmed by the 9,000 injured. Relief money poured in from all over the world, but the town was particularly touched by the help it received from Massachusetts. Even now, Halifax sends a Christmas tree every year to the city of Boston as thanks. Something maybe to think about as you wrestle yours down to the tip.