A flood of poppies in London

LONDON, England - It was a simple idea. Take the poppy, long a symbol of loss in war, and turn it into a commemoration worthy of the 100th anniversary of World War I - the war that was supposed to end all wars, but didn't.

And so, for each British and Empire soldier who died in that war, a ceramic poppy has been "planted" in what used to be the moat of the ancient Tower of London. And the result has astonished and captivated a nation.

Seen from the air, it is a sea of sacrifice; a flood of blood.

And, for the crowds who have come in the hundreds of thousands to witness it, it has been a lesson no history book can teach.

"It just brings home the number of lives that were lost," said Derek Whitlock. "Some might say wasted."

"These are only the British Commonwealth losses," said John Wells. "They're not the German losses. They're not the American losses. And each one represents a life."

888,246 lives - a cascade of terrible beauty that shocks the eye as it tugs at the heart.

The Tower's ceremonial warders, like Chief Yeoman Warder Alan Kingshott, have never seen crowds like it. And he thinks he knows why.

"When you say '888,246,' it's a number," he said. "But when you see it physically on the ground, it has so much impact on you."

More impact, even, than the display's creator, theatrical set designer Tom Piper, imagined.

"It was never for me intended to be an illustration of war or the horrors of war," said Piper. "It's about commemoration and it's about the beauty of human life and the fragility of human life.

Each evening an honor roll of some of the names of the dead is read out and the "Last Post" is played.

And a hundred years later, a nation keeps its promise to remember them.