In 1945 he joined the Dutch Ministry of Transport, moving to the Ministry of Economic affairs in 1946. In 1947 he was Secretary to the Dutch national delegation at the first Paris conference on the Marshall Plan. Between 1957 and 1958 he was statesecretary for foreign affairs for the Labour Party in the fourth Cabinet Drees. He took over as permanent secretary of the Bilderberg Group in 1960, upon the death of Józef Retinger. From 1961 to 1963 he was president of Dutch airline KLM. From 1966 to 1984 he was professor of international relations at Leiden University.