In September 1940 the Dutch abstract artist Piet Mondrian arrived in New York, a refugee from war and the London Blitz. He was 68, a well known figure in modern art circles in Europe but as yet little appreciated on the other side of the Atlantic. His visas, his travel and his accommodation had been sorted out for him by well-wishers in Britain and he was welcomed in America by Harry Holtzman, an artist some 40 years his junior.