[1] Jebb entered the British Diplomatic Service in 1924 and served in Tehran, where he got to know Harold Nicolson and Vita Sackville-West.

She was a granddaughter of the gun-developer Sir Andrew Noble, 1st Baronet, and a great-granddaughter of Isambard Kingdom Brunel.

On his return to the Foreign Office, Jebb asked to be posted to Madagascar, but this application was rejected, and he was sent to the Treasury for economic training.

He represented the United Kingdom at the Brussels Treaty Permanent Commission with personal rank of ambassador.

[4] In the latter role, he was angered that secret negotiations between the British, French and Israelis in advance of the Suez invasion in 1956 took place at Sèvres without his knowledge and, in certain respects, that he was sidelined by Prime Minister Harold Macmillan at the Paris "big power" summit in 1960.

On 12 April 1960 Jebb was created a hereditary peer and as Baron Gladwyn, of Bramfield in the County of Suffolk.