 From 1920, Clark was appointed to Northern Ireland as assistant under-secretary – the equal in the six counties to Sir John Anderson, the head of the Dublin Castle administration – and was instrumental in resolving amicable relations between Northern Ireland and the newly formed Irish Free State.His friendship with James Hamilton, 3rd Duke of Abercorn, the Governor of Northern Ireland, also eased relations between the new Irish government and Downing Street.Clark was appointed a Knight Commander of the Order of the Bath in 1924.