On Tuesday, thousands of miles apart, in three great cities, London, New York and Los Angeles, 75 dancers will dance 100 solos in each venue in honour of the late iconoclastic choreographer Merce Cunningham, who would have turned 100 that day. It is a spectacularly ambitious wake for the choreographer who for 70 years denied dance a dramatic or expressive face, and threw all norms of beginnings, middles and ends, of meaningful sequence or physical logic, into a bonfire of expectations.