Born in 1915 Ridsdale was educated at Tonbridge and Sandhurst. In 1935 he joined the Royal Norfolk Regiment, later being attached to the British Embassy, Tokyo (1938-39). During the Second World War he served in the Royal Norfolk Regiment, Royal Scots, and Somerset Light Infantry. His postings included Assistant Military Attaché, Japan, 1940; GSO3, Far Eastern Section, War Office, 1941; GSO2, Joint Staff Mission, Washington, 1944-45. He retired from Army with the rank of Major in 1946.

During his post-war political career he unsuccessfully contested the North Paddington seat in the General Election of 1951, but later (1954-92) served as the Conservative Member for the Harwich Division of Essex. He acted as the PPS to the Parliamentary Under- Secretary of State for the Colonies, 1957-58 and PPS to the Minister of State for Foreign Affairs, 1958-60. He was appointed, successively, as the Parliamentary Under- Secretary of State at Air and Vice-President of the Air Council, 1962-64, and for Defence for the Royal Air Force, Ministry of Defence, April-October 1964.

Throughout his political career Ridsdale maintained extensive Japanese contacts, acting as Chairman of the British Japanese Parliamentary Group, 1964-92 and the leader of Parliamentary delegations to Japan, 1973, 1975, annually 1977-82 and 1988. He was a Member of the North Atlantic Assembly, 1979-92, being the Vice-President of the Political Committee, 1983-87.

He received the CBE in 1977 and was knighted in 1981. He died in July 2004. Papers include details of Julian Ridsdale's family life, including his wife, Dame Victoire Evelyn Patricia Ridsdale [1921 - 2009], known as Dame Paddy Ridsdale. The collection contains details of 'Paddy's' life as the wife of a Conservative Minister for Parliament with some mention of her role as chairwoman of the Conservative MPs' Wives club. The papers also include information about 'Paddy's' family, notably Sir Thomas Lopdell O'Shaughnessy [1850 - 1933], who was the last Recorder of Dublin in Ireland.