Roberts returned to London in 1937 to work in the central department of the Foreign Office, where, as a still relatively junior official, he was involved in much of the diplomacy with Nazi Germany in the lead-up to World War II.
[1] He was based in London until January 1945, when he was posted to Moscow, serving as an advisor to Winston Churchill at the Yalta conference and as British minister to the Soviet Union until 1947.
In the latter year, he was appointed Ambassador Extraordinary and Plenipotentiary to Yugoslavia, a post he held until 1957,[2] when he became British Permanent Representative on the North Atlantic Council to 1960.
He also developed a good relationship with the foreign leaders he dealt with, including Joseph Stalin, Josip Broz Tito, Konrad Adenauer, Willy Brandt, and Helmut Schmidt.
However, his role in the development of a close relationship between Britain and Germany did not lead to stronger German support for British membership of the European Economic Community.