He began his chess career at the age of 16, and he soon decided to become a full-time chess writer and player. Initially an over-the-board (OTB) player, he soon began to mix OTB play with correspondence play. He was a four-time winner of the Australian Chess Championship, in 1935, 1937, 1949, and 1951. He won the first two Australian Correspondence Chess Championships, in 1938 and 1945. He also won the New Zealand Chess Championship in 1924/25. In Auckland of 1952, Purdy drew a hard-fought match with Ortvin Sarapu, at the time by far the best player in New Zealand. They were thus declared Australasian co-champions.