I went to Chalk Farm last summer and while walking back to the tube station I saw this bit of graffiti.
Cleaning up Chalk Farm
It is kind of in the style of Banksy, but doesn't appear to be politically motivated like a lot of Banksy's stuff. I like the wit of the picture, which is what made me stop and take the photo.
Most of the wall was exposed after some of the concrete fell off. The artist painted the cleaner around that part and ehanced the brickwork with paint.