Time once again to decrapify the Thames. Each year, Thames21 organises a voluntary cleanup of the river. Old Father Thames is among the cleanest rivers to flow through a capital city, but he's still prone to a build up of bottles, trolleys and other unsightly jetsam. The operation to clean his banks begins tomorrow and lasts through till Sunday (12-15 August). The sites are in Brentford (Thursday), Isle of Dogs (Friday), Fulham (Saturday) and Erith (Sunday). Each date has its own Facebook signup, or you can just turn up on the day. Thames21 will provide all safety equipment, including reinforced wellies. If you happen to be away, there's another chance to tidy on Sunday 29 August down at Battersea.