Sometimes, early in their career an artist makes a body of work so powerful and singular, and so necessary, that it comes to define them, and critics end up measuring the rest of their work in its light. So it is with 68-year-old American artist Pope.L, whose belated first UK show now fills South London Gallery (SLG). In 1978, Pope.L crawled the length of New York’s 42nd street on his hands and knees, carrying a small potted flower as a sort of prop. He wore a thrift-store suit with a yellow square stuck to his back. Later, he went on to crawl from one end of Broadway to the other. He crawled around Tompkins Square Park and he crawled in Miami. These grim, high-endurance public performances made his name and bought with them a degree of both fame and notoriety.