He was Private Secretary to two Parliamentary Under-Secretaries of State for Foreign Affairs, Arthur Otway and Viscount Enfield, 1868–1874.
He accompanied Salisbury to the Congress of Berlin in 1878 and was given the diplomatic rank of Second Secretary for the purpose.
When Sir Edward Grey succeeded Lord Lansdowne as Foreign Secretary in December 1905 Barrington was appointed Assistant Under-Secretary for Africa, but retired in July 1907.
Barrington was appointed Companion of the Order of the Bath (CB) in the 1889 Birthday Honours.
[2] He was promoted to a Knight Commander (KCB) in the order in the 1902 Coronation Honours list published on 26 June 1902,[3][4] and received the knighthood in a private audience with King Edward VII on 2 August, during the King′s convalescence on board HMY Victoria and Albert.