A glass doorknob acted as a magnifying glass, focusing sunlight into a burning beam that torched some clothing and set fire to a bedroom in a south London home.
“The focal length from the window was just the right distance and it became the same principle as when you try to set fire to paper with a magnifying glass when you are a child,” The London Fire Brigade’s Charlie Pugsley told The Telegraph.
Apparently, a crystal ball and a mirror are to blame for similar fires in London this year.