Rydbeck began his diplomatic career as an attaché at the
Ministry for Foreign Affairs in 1939. The following year he served as a clerk to the
Committee on Foreign Affairs, and in 1940 he was posted as attaché to the Swedish legation in
Berlin. He was transferred to
Ankara in 1941, returned to the Ministry in 1942, and became acting second secretary in 1943. That same year he also joined the American Affairs Inquiry (
Amerikautredningen). From 1955 to 1970 Rydbeck was Director-General of
Sveriges Radio. He then served as
Sweden's Permanent Representative to the United Nations from 1970 to 1976, and as Sweden's representative on the
United Nations Security Council from 1975 to 1976. During this period he was appointed by the UN Secretary-General to negotiate the future of
Western Sahara. He was Swedish ambassador in
London from 1977 to 1979 and Director-General of
UNRWA in
Vienna from 1979 to 1985. In 1987 he chaired the national citizens’ commission reviewing certain arms export practices. Rydbeck also held a wide range of board and leadership positions in cultural, academic, and international organizations. He was a board member of the
Swedish Institute and the Swedish-American News Agency from 1953 to 1955, the Swedish Tourist Traffic Association (
Svenska turisttrafikförbundet) (1953–1955), and the Stockholm Concert Association (
Stockholms konsertförening) (1955–1962). He served on the national board of the
Swedish Red Cross (1955–1970), the council of the Swedish Institute from 1956, and the National Swedish Psychological Defence Planning Committee (
Beredskapsnämnden för psykologiskt försvar) (1954–1970), where he was vice chairman from 1962 to 1970. He chaired the
FHS Association (1957–1970), was president of the
European Broadcasting Union (1961–1964, later honorary chairman), and chairman of the International Institute of Communications (1967–1970). He also served on the boards of the
Tidningarnas Telegrambyrå (TT) and the
Swedish Institute of International Affairs from 1967. In addition, he was a member of the
Sällskapet Idun. ==Personal life==