Update: This seems to have become quite a popular photo which is ironic since it was taken to illustrate a no longer genuine Banksy. Also there are much better pictures of this particular piece on flickr.
Incidentally, the footballer next to it probably isn’t and never was by Banksy. I saw a card on sale at the library that claims it is.
Another update: a much better Banksy related photo that I took: www.flickr.com/photos/barnoid/4449367540/
Taken through a circular polariser to reduce reflection from the water.