Fuller's Frontier "#FindFlavour" by The Corner

Fuller's has hidden messages in what appear to be blank posters, which can only be revealed via Instagram.

The campaign for Fuller's Frontier craft beer has fly-postered locations around Hackney in east London.

Each poster has an image or message subtly embedded into the artwork. Participants must take a picture of the poster and upload it to Instagram, where they will have to adjust the filters to reveal a secret message that may win them a prize.