If you missed the last Banksy mini walking tour that photographer Martin from Shellshock organised, then you are in luck as he has planned a fourth for next month.
The fourth walking tour is planned for Sunday 24th September 2006 and will cover the Shoreditch area. The 2pm start on the 24th which I believe is a Sunday, should allow more people to take part in the tour.
There is no charge for the tour and you do not need to book a place, just turn up on the afternoon. Meeting point details for the afternoon can be found on the Banksy Flickr page.