Photography on a Postcard is offering the chance to own a signed, one-off print by a world-renowned photographer for just £55 at Photo London. The twist is that the photographer will remain anonymous until after the sale. Buyers can choose from 350 postcard-sized prints, and the photographers involved include Bruce Gilden, Mark Power, Dougie Wallace, and Laura Pannack, as well as 35 hand-selected emerging image-makers. Buyers will be able to choose their postcard-sized print in person, but priority will be given to those who pre-register online. All money raised will go to the Hepatitis C Trust and its campaign to eliminate the virus from the UK by 2025.