What's with the poppy?

I see from my referral logs that I have gotten many Google hits from people searching for "poppy pin on prince charles lapel" and similar queries. I assume people are wondering what's with his colourful lapel pin:

In countries of the British Commonwealth, November 11 is Remembrance Day, marking the armistice that ended World War I in 1918. (In Great Britain, the main day of observance is the nearest Sunday.) While not a general holiday everywhere it is observed, it is still a day of solemn ceremony to honour our war dead. Amongst other ceremonies, two minutes of silence is observed at the eleventh hour of the eleventh day of the eleventh month, the time of the armistice.

Poppies proliferate in Flanders Fields in Belgium, where many war dead are buried. The most famous poem of World War I, "In Flanders Fields" by Canadian solder and physician John McCrae, uses the poppy as a symbol for the dead:

In Flanders fields the poppies blow
Between the crosses, row on row,
That mark our place; and in the sky
The larks, still bravely singing, fly
Scarce heard amid the guns below.

In the weeks prior to Remembrance Day, veterans' groups sell poppy pins for a small donation. In the five years since the unknown soldier was interred at the foot of the War Memorial in Ottawa, it has become customary for spectators at the Canadian national Remembrance Day observance to leave their poppies on top of the sarcophagus at the end of the ceremony.

So, for the sake of any future Googlers, that is the reason why the Prince of Wales is sporting a cheap plastic poppy on his expensive, tailor-made suit.