[2] Having attended Royal Military College, Sandhurst, Cadogan was commissioned on 1 February 1934 as a second lieutenant in the Coldstream Guards, British Army.
[5] On 12 April 1937, he transferred from the Coldstream Guards to the Royal Wiltshire Yeomanry, Territorial Army, in the rank of second lieutenant.
[7] On 4 February 1943, as a lieutenant (temporary captain), he was awarded the Military Cross (MC) "in recognition of gallant and distinguished services in the Middle East".
[10] Cadogan held the office of Deputy Lieutenant (DL) of the County of London in 1958 and was Mayor of Chelsea in 1964.
Cadogan married twice; firstly, on 11 June 1936 Primrose Lilian Yarde-Buller, daughter of John Reginald Lopes Yarde-Buller, 3rd Baron Churston of Churston Ferrers and Lupton and secondly Cecilia Margaret Hamilton-Wedderburn (10 March 1916 – 31 March 1999),[11] daughter of Lt-Col. Henry Kellerman Hamilton-Wedderburn, on 13 January 1961.