Gustav Metzger

Crawling under a sheet, the image printed on the floor slowly reveals its fearful symmetry: a handful of Austrian Jews being forced to scrub the streets of Vienna in 1938 stare back, also on all fours, only inches from your face. Behind a sacking sheet hides another grainy, blown-up photograph, this time of Palestinians shot dead on their way up Temple Mount in Jerusalem in 1990.

There are more 'Historic Photographs', of a Warsaw Ghetto child emerging from a brick wall and, we're told, a parade of salutatory Hitler Youth - although this one's completely concealed between two welded sheets of plate metal. The 83-year-old artist responsible for these compelling acts of disclosure and censorship is Gustav Metzger, who has lived in exile from his native Nuremberg since his Polish-Jewish family was variously killed or dispersed by the Nazis.

As the London art world's perennial outsider, Metzger has long been a hard sell, so hard in fact that he's struggled to make a career out of his life's work. His reticence to engage with the value structures of the art market has been matched only by his dogged refusal to compromise his radically oppositionist practice (giving up art altogether from 1977-80 was one such ideological stand). He became known in 1960 for his 'Auto-Destructive Art' manifesto urging the use of 'Ballistics, Explosives, Glass, Mass Production, Pressure, Stress', which was complemented by his acid-flinging, canvas-dissolving performances on the South Bank.

Those were violent actions for a time overshadowed by wars and nuclear threats but his later work is no less politically charged. He's turned his wrath towards the automotive trade in 'Kill the Cars' (before they kill us, being the implicit message of his beaten-up banger) and climate change (long before we caught on) in his up-turned trees, their branches suffocated by concrete blocks.

This is a frugal but richly deserved show, reacquainting the public with a living legend but also reflecting the man and his unfortunate hobo-like existence - the reams of newspapers he has collected over the past two decades litter the first gallery as a monument to the permanence of belongings as opposed to the transience of an existence in which we'll all eventually turn to mulch.