Rendel entered the
Diplomatic Service and was the head of the Eastern Department of the Foreign Office from 1930 to 1938. In 1922 he produced a seven-page British Foreign Office document which detailed the persecution of Greeks and other minorities in the
Ottoman Empire. The document drew on official reports and eyewitness testimonies by personnel who were present. Rendel stated that throughout the
First World War, "it is generally agreed that about 1,500,000 Armenians perished in circumstances of extreme barbarity, and that over 500,000 Greeks were deported, of whom comparatively few survived". He then went on to describe further massacres and deportations of Greeks in the period after the
Armistice. In 1937 he and his wife, Geraldine (1884–1965), crossed
Saudi Arabia. Geraldine was the first
European woman to be received for dinner at the royal palace in
Riyadh. Rendel said of Riyadh: :"...it was a revelation to me of how fine in line and proportion modern Arabian architecture can be"." Rendel was His Britannic Majesty's Envoy Extraordinary and Minister Plenipotentiary to
Bulgaria, but the
United Kingdom broke off diplomatic relations as the country joined the
Tripartite Pact and thus became a close ally of the
Nazis. It fell to Rendel to take his staff of 50 by train to
Istanbul,
Turkey. His party was caught in a huge bomb explosion at the
Pera Palace Hotel. Rendel was upstairs when the bomb in the baggage room exploded with devastating consequences. His daughter Ann, then 21 and acting as Legation Hostess, was knocked down and slightly injured. In all, there were four deaths and 30 injured. It was later claimed by the Germans that various bombs had been placed in the Legation's luggage before it had left
Sofia. In 1941, he was appointed
Envoy Extraordinary and Minister Plenipotentiary to the Kingdom of Yugoslavia, a post held until 1943. He was
knighted in the latter year and served as Ambassador to
Belgium between 1947 and 1950. Rendel headed a commission in 1953 to recommend further changes in the constitutional system that helped created the
Constitution of Singapore under the Singapore Colony
Order in Council 1955. Rendel also served on various
United Nations committees. Though officially
retired, he continued to be employed by the Foreign Office until 1964. ==Personal life==