 Kerr supervised the handover of Ulcinj to Montenegro to allow Montenegro an outlet to the sea in accordance with the terms of the Treaty of Berlin in September 1880.He became Captain of the Medway Steam Reserve in December 1881 and naval private secretary to Lord George Hamilton, First Lord of the Admiralty in July 1885.Promoted to rear admiral on 1 January 1889, Kerr became Second-in-Command of the Mediterranean Fleet, hoisting his flag in the battleship HMS "Trafalgar" in April 1890 and then in the cruiser HMS "Amphion" in April 1892.