This is one of many vitreous enamel plaques that have recently appeared in tube stations, looking oddly official, perhaps because enamelled steel is used for most of the Tube maps and signs. They are in fact works of art, perhaps something to make up for the advertising excesses on the Underground. There will be 270 plaques when the project is completed, with a different design on each. They are all similar - a black labyrinth on a white background with a small red detail and a number - but each is unique. The designs, and presumably the original idea, are by artist Mark Wallinger, perhaps best known for his contribution to the Fourth Plinth, a naked figure with a crown of barbed wire (apparently - I completely missed it and just found that on Wikipedia). Nice to see cash-strapped London Underground can still spend money on art, and can still do it this well.