The shape, size and styles of doors tell us a lot about what lies behind them. Heavy wood with some ornate metalwork probably leads into a cavernous stone church; a smart one-tone paint job no doubt guards a Georgian or Victorian townhouse, and so on.
As this selection shows, London has some grand old doors. But the best doors are the dingy ones, of which there are plenty in a city of dark corners and alleyways. Our leading image here channels that spirit.
With thanks to Londonist Flickr pool contributors: laurabot_, Gareth L Evans, tezzer57, fabiolug, makipong, Matthew Gidley, fabiolug, richwat2011, PaulitzerPix and curry15.