 Complete the following phrase:  In 1991, tutors at the Royal College of Art refused to present Gavin Turk with his postgraduate degree, a decision based on his graduation exhibition. Titled Cave, it consisted of a whitewashed studio space, containing a blue heritage plaque of the kind normally found on historic buildings commemorating his own presence as a sculptor, stating Gavin Turk worked here, 19891991. This bestowed some instant notoriety on Turk, whose work was collected by numerous collectors including Charles Saatchi, who later exhibited Turks work in the exhibition 