Not a maze but a labyrinth, the London Tube celebrates its 150th birthday with art project.

If you live in or have just recently visited London and travelled on the underground, it’s very likely that you may have spotted out the corner of your eye, hanging very inconspicuously on a wall or column a small square black and white enamel artwork of a labyrinth?

Their creator is the artist Mark Wallinger, winner of the Turner prize in 2007 for State Britain, his recreation of Brian Haw's Parliament Square protest shown on the central galleries of Tate Britain, who insists that they are not mazes but labyrinths. The difference he says is that mazes are confusing, exasperating and easy to get lost in. However labyrinths have one way in, one way out.

In all there are now 270 of the black and white enamel artworks hanging in the various tube stations around London. The Labyrinth project was two years in the making and has become London Underground’s largest ever art commission.

Tamsin Dillon, head of Art on the Underground, said the tube system represented one of the best public spaces for art in the UK. "Something like 4 million people every day have an opportunity to encounter the art works that we commission with a billion people, every year, using the network."

Every station will have an enamel panel measuring 60cm by 60cm with a different labyrinth on it, each made by the company that does all the network's enamel signage.

Wallinger hopes it will bring out the geek in tube enthusiasts as they travel around the network in order to view all 270, and it is estimated that it will take more than 16 hours to do so in person.

Maybe an easier way to see them all is to get hold of a copy of the book Labyrinth: A Journey Through London’s Underground. The beautiful 320 page hardback book costs £24.99 and is definitely on this year’s Yellow Hats Christmas list