Chris Martin (from The Sun newspaper May 13, 2008): "It's our attempt at a Smiths song. It's about witch drownings. I was interested about that period in London where people were supposedly drowned for being a witch. And that's where that song came from. About being accused of something you didn't do."
Coldplay recorded this song in a Barcelona church, which provided the distinctive echo.
For more info go to http://www.songfacts.com/detail.php?id=11581