By Yoho2001 at the English-language Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=6769190
Okay, I admit it. I love fanlights.
I’m talking about the fanlights you see above Georgian townhouse doors like the ones on Buckingham Street near the Strand.
They were first introduced in the early 18th Century in order to let more light to enter previously dark hallways.
Consisting of a curved or arched top window above the main entrance door, designs were usually delicate with thin glazing bars of wood or zinc, creating a simple radiating ‘fan’ effect. As metal work techniques improved, so elaborate designs started to appear.
A great secret fact about fanlights? Before they thought of the idea of house numbers, houses were identified by the pattern on their fanlight window. (Just think of the poor old postman having to remember all those intricate designs!)