 He was appointed a Knight Grand Cross of the Royal Victorian Order on 20 May 1937.Advanced to Knight Grand Cross of the Order of the Bath in the 1938 New Year Honours and appointed First and Principal Naval Aide-de-Camp to the King on 1 July 1938, Blackhouse became First Sea Lord on 7 September 1938.Taking office shortly before the signing of the Munich Agreement, his major contribution as First Sea Lord was to abandon the official British policy of sending a major fleet to Singapore to deter Japanese aggression (the Singapore strategy), realising the immediate threat was closer to home (from Germany and Italy) and that such a policy was no longer viable.