Sir John Margetson KCMG (born 9 October 1927) is a former British Ambassador to Vietnam, the United Nations, and the Netherlands.
John William Denys Margetson is the younger son of the late Very Rev. William Margetson and Marion Jenoure. He was educated at Blundell's School and St John's College, Cambridge, where he was a choral scholar. From 1947–49 Margetson served his National Service with the Life Guards regiment of the Household Cavalry.
Margetson’s later career included appointments as British Ambassador to Vietnam 1978–80, deputy Permanent Representative to the United Nations (with rank of ambassador) 1983–84, and ambassador to the Netherlands 1984–88. He was appointed CMG in 1979 and knighted KCMG in 1986.
Following his retirement from the Foreign Office, Margetson devoted himself to various charities and was chairman of the Royal School of Church Music 1988–94, of the Yehudi Menuhin School 1990–94, and of the joint committee that manages the Royal College of Music and the Royal Academy of Music 1991–94. He served as Gentleman Usher of the Blue Rod from 24 July 1992 – 25 October 2002.
- MARGETSON, Sir John (William Denys), Who's Who 2014, A & C Black, 2014;online edn, Oxford University Press, 2014
- Interview with Sir John Margetson, British Diplomatic Oral History Programme, Churchill College, Cambridge
|Ambassador to Vietnam
Sir Philip Mansfield
|Ambassador to The Netherlands
Sir Michael Jenkins
Sir John Moreton
|Gentleman Usher of the Blue Rod
Sir Anthony Figgis