Only a min walk from my work is where they did a Banksy project where the public got to turn a street (is really a tunnel under Waterloo station) in to an art exhibition.
It's pretty damn cool, here's a few snaps I took on my phone as I wandered through:
The following two pics are actually made by carving out the plaster:
I really recommend checking it out when you're in Waterloo some time, it's much cooler in real life!
By Tony Baker: email