Robert Gilbert Vansittart, 1st Baron Vansittart, GCB, GCMG, MVO, PC, known as Sir Robert Vansittart between 1929 and 1941, was a senior British diplomat in the period before and during the Second World War. He was Principal Private Secretary to the Prime Minister from 1928 to 1930 and Permanent Under-Secretary at the Foreign Office from 1930 to 1938 and later served as Chief Diplomatic Adviser to the British Government. He is best remembered for his opposition to appeasement and his strong stance against Germany during and after the Second World War. Vansittart was also a published poet, novelist and playwright.