No, you're not hallucinating. This eerie glowing face peering out from street railings in central London is, in fact, a new Amnesty International campaign entitled, Making The Invisible Visible....

The campaign is the fruit of a collaboration between London agency Brothers and Sisters' creative team Lisa Jelliffe and Kirsten Rutherford (the duo behind the StreetMuseum iPhone app for The Museum of London) and Berlin-based street art collective, Mentalgassi.

The point of the campaign is to raise awareness of Amnesty's work seeking justice for unfairly treated or imprisoned people around the world, and in particular, of the plight of Troy Anthony Davis (it's his face peering out from the installations), a 42 year old man who has spent the last 19 years on death row in the US state of Georgia for a murder he has always said he did not commit. Amnesty International maintain that no physical evidence links Davis to the crime and seven out of nine witnesses on whose evidence he was convicted in 1991 have since changed or retracted their testimony, some citing police coercion. Despite the doubts surrounding his guilt, he still faces execution.

The image is, of course, made up of strips stuck to the side face of square tube railings - meaning the image isn't visible when you look at the railings head on, but only when you see the railings from a side view - as you're walking towards them.

"The surprising use of faces on fence railings reminded us of prison bars which seemed like a unique way to highlight Amnesty's work," says Jelliffe of the campaign.

For those in London wanting to check out the installations in the flesh, there are two on railings along Great Pulteney Street in Soho, and another outside 5 Berners Street, just north of bustling Oxford Street.

A plaque on each site alerts passers-by to an Amnesty website – amnesty.org.uk/fence – where they can sign a petition calling for justice for Davis.

Here's a video of the pieces being installed:

Troy Davis: Making the invisible visible from Amnesty International on Vimeo.

amnesty.org.uk/fence