WHEN JON Langford was at art school – University of Leeds, the college he refers to below – it was right around the time that TJ Clark showed up. Clark, the Marxist art historian and one-time only British member of the Situationist International, apparently did a lot to pull the university’s art college away from its staid and stale academic approach to art. Langford, in other interviews, has jokingly likened him to a Che Guevara figure for the art department.