He was educated at Heatherdown School, Eton College and Christ Church, Oxford, and was called to the bar in 1931.

They had two sons: The couple became leaders of the London artistic and social scene and were dedicatees of Evelyn Waugh's second novel Vile Bodies.

However, they divorced in 1933 after Diana deserted Guinness for British fascist leader Sir Oswald Mosley.

In November 1944, Guinness succeeded to the barony when his father, posted abroad as Resident Minister in the Middle East by his friend Winston Churchill, was assassinated in Cairo.

With Frank Pakenham he sought the return of the "Lane Bequest" to Dublin, resulting in the 1959 compromise agreement.