Ulrich Friedrich Wilhelm Joachim von Ribbentrop (1893-1946) was Foreign Minister of Germany between 1938 and 1945, and German Ambassador to Britain during 1936/37.
Following the war he was tried at Nuremberg and sentenced to death by hanging for war crimes.
During his time as Ambassador in London, he is said to have committed the social gaffe of greeting King George VI with a Heil Hitler salute. Whilst he was in London, it was also rumoured that he was romantically involved with Wallis Simpson who became the Duchess of Windsor in June 1937 following her marriage to the former King Edward VIII. However in her memoirs, published in 1956*, the Duchess of Windsor denied any such involvement.
* WINDSOR, Wallis: The Heart has its Reasons: The Memoirs of the Duchess of Windsor (Bath: Chivers Press, 1956).