A musket ball punched through the deck of HMS Victory just before half-past one on 21 October 1805. It struck Admiral Horatio Nelson in the left shoulder, drove through his spine, and lodged in his back. He murmured to the men who carried him below: "They finally succeeded, I am dead."

The battle that brought Nelson to that moment had been years in the making. Napoleon Bonaparte controlled most of Europe by land but could not cross the English Channel so long as Britain's Royal Navy held it. His plan was to draw the British fleet away, mass French and Spanish warships in the Channel, and open a corridor for his invasion barges.

Vice-Admiral Pierre-Charles Villeneuve commanded the combined Franco-Spanish fleet. He was an anxious, reluctant commander, scarred by an earlier defeat at the hands of the British, and his crews were badly undertrained. When Nelson's fleet arrived off Cádiz in late September 1805, Villeneuve's captains voted to stay in harbour.

What forced them out was humiliation. Word reached Villeneuve on 18 October that a replacement admiral was already in Madrid with orders to relieve him. Rather than be disgraced before his fleet, he ordered the combined force of thirty-three ships to sea immediately.

Nelson had twenty-seven ships against thirty-three, and his opponents carried more guns. His answer was to abandon the standard line-of-battle entirely. He would split his fleet into two columns and drive them straight at the allied line, cutting it into pieces and forcing a close-range brawl where British gunnery and seamanship would decide things.

At 11:45 that morning, he sent his famous signal from Victory's masts: "England expects that every man will do his duty." Then the two British columns bore down on the allied line, their bows exposed to raking fire for nearly an hour before a single gun could answer.

Victory punched through the line just astern of Villeneuve's flagship Bucentaure, unleashing a treble-shotted broadside through her stern that killed or wounded up to four hundred of her eight hundred men and knocked her out of the fight in a single volley. The allied centre collapsed.

Nelson was shot minutes later. He was carried below and died at half-past four that afternoon, three hours after being hit, having learned the battle was won. His last recorded words were "God and my country." The British took twenty allied ships and lost none.

Villeneuve was captured aboard the wrecked Bucentaure and later brought to Britain as a prisoner. He attended Nelson's state funeral while on parole. Returning to France in 1806, he was found dead in his inn room with six stab wounds in his chest; it was officially recorded as suicide.

The victory ended any French hope of challenging Britain at sea. Napoleon's empire would grind on for another decade, but he never again threatened an invasion. Nelson was carried home preserved in a barrel of brandy, given a state funeral, and commemorated across Britain and its empire. London's Trafalgar Square still bears the name of the battle he won at the cost of his life.