Career
Lord Lieutenant of Northumberland from 1956 to 1984
Chancellor of the University of Newcastle from 1964 to 1988
Chairman of the Medical Research Council from 1969 to 1977
President of the Royal Agricultural Society of England in 1956 and 1962
Chairman of the Agricultural Research Council from 1958 to 1968
Chairman of the Committee of Enquiry on Foot and Mouth Disease
Lord Steward of Her Majesty Household from 1973 to 1988
Master of the Percy Foxhounds from 1940 to 1988
He was commissioned into the Northumberland Hussars. In 1940, as a Lieutenant, he transferred to the Royal Artillery. In 1947, as a Captain, he transferred back to the Northumberland Hussars.
Northumberland married Lady Elizabeth Diana Montagu Douglas Scott (died 19 September 2012), daughter of Walter Montagu Douglas Scott, 8th Duke of Buccleuch, on 12 June 1946.
They had seven children:
Lady Caroline Mary Percy (b 3 May 1947), married Pierre, Comte de Cabarrus on 12 January 1974 and had issue:
Chiara de Cabarrus (22 November 1974)
Diana de Cabarrus (1977)
Lady Victoria Lucy Diana Percy (b 19 April 1949), married John Cuthbert on 4 October 1975 and divorce had issue. Then remarried to Charles Lyon Fellowes in 2000 and divorce in 2006.
Alice Cuthbert (1978)
Lucy Cuthbert (1982) married Prince Khalid of Saudi Arabia) on 28 March 2011. Molly Cuthbert (1984)
David Cuthbert (1987)
Lady Julia Helen Percy (b 12 November 1950), married Nicholas Craig Harvey on 11 June 1983 and had issue:
Georgina Craig Harvey (20 May 1986)
Christopher Craig Harvey (4 October 1988)
Laura Craig Harvey (7 September 1992)
Henry Alan Walter Richard Percy, 11th Duke of Northumberland (1 July 1953 – 31 October 1995)
Ralph George Algernon Percy, 12th Duke of Northumberland (b 16 November 1956), married Jane Percy, Duchess of Northumberland (née Jane Richard) and had issue
Lady Louise Percy (25 May 1962 – 27 May 1962)
Lord James William Eustace Percy (b 18 June 1965), married Lucy Caroline Rugge-Price and had issue:
Thomas Hugh Percy (29 April 2001)
Eliza Rose Percy (21 February 2003)
Willa Katherine Percy (20 April 2005)
Samuel James Edward Percy (31 March 2008).