His father was raised to the peerage as Baron Egremont in 1963, the same year as his grandfather succeeded to the Leconfield barony, inheriting it from his older brother.

He was educated first at Heatherdown School near Ascot, then at Eton College and at Christ Church, Oxford, where he read modern history.

His biography of Major General Sir Edward Spears, Under Two Flags, was published in 1997 and was short listed for the Westminster Medal for Military History.

Egremont's Siegfried Sassoon came out in 2005 and was short listed for the James Tait Black Memorial Prize.

Egremont married Caroline Nelson, a garden designer, granddaughter of Almeric Paget, 1st Baron Queenborough, in 1978.