Although street art is deeply connected with gentrification, it often gives a voice to the precisely the victims of it. The spray-painted murals adorning the walls of Madrid speak truths – truths that the passionate graffiti hunter Gerardo taught me how to read. In the secret messages left behind by graffiti writers, I saw not only themes of suffering and discrimination but also a growing backlash against them.

La cárcel de Carabanchel, Europe’s biggest and most notorious prison until its closure in 1998, was built under General Franco’s watch. Between 1940 and 1944, every wall was raised and every metal door was fitted by the same prisoners who would eventually do their time here. None dared lay a brick loosely or leave a screw untightened – this prison was a star-shaped fortress, and nobody was escaping.