They signed up together to fight in World War I. Lupton's sister Olive Middleton was the great grandmother of Catherine Middleton[4] who married the great-grandson of Lord Spencer, Prince William, in April 2011.

[11] On 27 August 1924, Lord Spencer was appointed the Honorary Colonel of the 4th (Territorial) Battalion, Northamptonshire Regiment,[12] remaining in that role when it was renamed 50th (Northampton Regiment) Anti-Aircraft Battalion on 1 October 1937,[13] and throughout its various post-war incarnations[14] until finally relinquishing his appointment on 1 April 1967.

[21] Lord Spencer was active in the local politics of Northamptonshire as a Conservative councillor.

He opened his ancestral home, Althorp, to the public and was a well-known art connoisseur, being a trustee of the Wallace Collection and chairman of the Royal School of Needlework.

Lord Spencer married Lady Cynthia Hamilton, second daughter of the 3rd Duke of Abercorn, on 26 February 1919 at St. James's Church in Piccadilly, London, and they had two children: Lord Spencer died at St Matthews Nursing Home, Northampton, after a short illness,[24] and was succeeded by his son, John, the father of Diana, Princess of Wales.