He was the brother-in-law of Diana, Princess of Wales, and a maternal first cousin of Ronald Ferguson, the father of Sarah, Duchess of York.

He was the son of Sir William Albermarle Fellowes (1899–1986), a major in the Scots Guards and land agent of the Sandringham estate, and his wife Jane Charlotte Ferguson (1912–1986).

[11][12] Fellowes left his position in February 1999 to return to private banking, his retirement having been announced implicitly on 1 June 1998 when his successor Robin Janvrin was named.

He was created a life peer on 12 July 1999 taking the title Baron Fellowes, of Shotesham in the County of Norfolk in the Queen's Birthday Honours List.

Lord Fellowes remained technically a member of the royal household, having been appointed an extra equerry to the Queen following his retirement.

[21] On 20 April 1978, Fellowes married Lady Jane Spencer, elder sister of Diana, Princess of Wales, at the Guards' Chapel, Wellington Barracks.