Egads! I've lived right around the corner of Notting Hill Tube station, if I had only known that these hidden gems were there, I might have been in jail for trespassing right now. ;)
The London Underground have stumbled onto a time capsule in a disused area of the Notting Hill Tube station. The area is inaccessible, but they did the right thing and had someone photograph the colorful graphic lovely that advertising once was. So very hip, isn't it? And the posters colors have held up surprisingly well. See the Flickr pool: Hidden posters of Notting Hill Gate Tube station to get your Retro on.
Hat tip @kishi