You can be part of this, and choose from 2 photographic scavenger hunts - one in East London and one in Croydon. You'll need a Flickr ID to register and the event may involve travel so make sure you have your Oyster Cards ready!
They're happening on Saturday 9th October with an 11am start. Places are limited, so to book your place contact Jane or Michelle at firstname.lastname@example.org with your Flickr ID and let them know which location you'd like to explore. More details are available at the Overground Uncovered Flickr Scavenger Hunt site.