As relations between Britain and Japan continued to deteriorate Sansom's reputation as a Japanophile came to be perceived as a liability. Although the Ambassador, Sir Robert Clive, continued to rely on Sansom, his successor from 1937, Robert Craigie, was less receptive to his advice. In 1935 Sansom took a leave of absence of six months, which he spent at Columbia University in New York as a lecturer. While he was on leave in London he announced his retirement from the Diplomatic Service with effect from September 1940. He agreed to return to Japan for one more mission before taking up a position waiting for him at Columbia University.