Sir John William Denys Margetson KCMG (9 October 1927 – 17 October 2020) was a British diplomat who served as ambassador to Vietnam, the United Nations, and the Netherlands.
He was educated at Blundell's School and St John's College, Cambridge, where he was a choral scholar.
From 1947 to 1949, Margetson served his National Service with the Life Guards regiment of the Household Cavalry.
He served as Gentleman Usher of the Blue Rod from 24 July 1992 – 25 October 2002.
[4] In 1963, Margetson married Miranda, daughter of Sir William Coldstream.