Commanding until 1977, Sinclair soon rose to higher administrative and directive roles in the navy, serving as commander of in 1978, Director of Naval Plans from 1979 to 1980, Director-General of the Military Staff Branch Strategic and International Policy Division Department of Defence from 1980 to 1982 and Chief of Staff and Deputy to the Naval Support Commander from 1983 to 1984. Sinclair was Chief Project officer during the establishment of the tri-service Australian Defence Force Academy, serving as its first commandant from 1984 to 1986. In the 1986 New Year Honours list, Sinclair was made an Officer of the Order of Australia (AO) for "Service to The Royal Australian Navy, particularly as the First Commandant of the Australian Defence Force Academy".Citation: "AO/NY86 For Service to The Royal Australian Navy, particularly as the First Commandant of the Australian Defence Force Academy.".</ref> In 1987 he was appointed Flag Officer Commanding HM Australian Fleet, a position which later changed to Maritime Commander, Australia.