Kennedy entered the Foreign Office in 1852. He served chiefly in the commercial branch, attaining the senior clerkship there early in the 1870s. This was his substantive appointment for many years, but he was almost constantly engaged on special services abroad, in particular:
His first deputation (1870–71) was to the Levant as president of a commission of inquiry into the Consular establishments
British Commissioner in Paris in connection with the Treaty of Commerce and Navigation (concluded with the newly established republic in 1872)
On several occasions questions relating to interchange of commerce between Great Britain and France took him to Paris, the last of them being when he assisted Sir Charles Dilke then Under-Foreign Secretary, to negotiate the subsisting Treaty.
In conjunction with Sir Edward Malet, the arrangements with Italy in 1875 for the renewal of the commercial treaty signed eight years before.
The Joint Channel Tunnel Commission
Commission of commerce and industry at Brussels in 1880
Senior British delegate to the North Sea Fisheries Conference in 1881 at The Hague (and was appointed plenipotentiary for the signature of the resulting Convention)
Senior British delegate to various international conferences on the protection of submarine cables held in Paris from 1882 to 1886 (Kennedy contributing powerfully to the resulting settlement)
Representing Great Britain at a conference at The Hague for the restriction of the liquor traffic in the North Sea
Representing Great Britain in the negotiations in Paris regarding the Channel Fisheries.
Years earlier he had edited "Kennedy's Ethnological and Linguistic Essays" and was chairman of the Exmouth School Board from 1896 to the dissolution of separate school authorities under the Education Act 1902. He was an active member of the council of the Society of Arts.
