Jackson went on to be Third Sea Lord and Controller of the Navy in February 1905 and, having been appointed a Naval Aide-de-Camp to the King on 12 September 1905, he was promoted to rear admiral on 18 October 1906. Appointed a Knight Commander of the Royal Victorian Order on 9 November 1906, he became Commander of the 6th Cruiser Squadron in the Mediterranean Fleet, hoisting his flag in the armoured cruiser HMS "Bacchante", in October 1908. He was awarded the Grand Cross of the Spanish Order of Naval Merit on the occasion of the visit of his flagship to Valencia in May 1909.