On leaving Princes, where he had studied with his father, James Ashton, William Ashton travelled to the UK, where, like his contemporary Hayley Lever, he undertook studies and painted in Cornwall. It was during this time that some of the major works of William Ashton in the School collection were painted.
Ashton is best known for his landscape works and, in recognition of his skills in this field, he was awarded the Wynne Prize, which is the premier prize for this genre, in 1908, 1930 and 1938. From 1937 to 1944 he was Director of the Art Gallery of New South Wales, one of the nation's finest collections.
Conventional honours came his way with an OBE in 1941 and a knighthood in 1960. In the world of art he was recognised by the Royal Society of British Artists for his efforts in advancing Australian Art, and was made an honorary member of the Royal Institute of Oil Painters. Sir William maintained a strong interest in his old school until his death, aged 82.