Prime Minister of Australia prime minister, otherwise William McMahon63. Robert Menzies was the oldest person to ever be prime minister, leaving office at 71 years old. The longest-serving Prime Minister was Sir Robert Menzies, who served in office twice: from 26 April 1939 to 28 August 1941, and again from 19 December 1949 to 26 January 1966. In total Robert Menzies spent 18 years, 5 months and 12 days in office. He served under the United Australia Party and the Liberal Party respectively. The shortest-serving Prime Minister was Frank Forde, who was appointed to the position on 6 July 1945 after the death of
Principal Secretary to the Prime Minister of Pakistan Principal Secretary to the Prime Minister of Pakistan The Principal Secretary to the Prime Minister of Pakistan (also referred to as PSPM) is the administrative head and highest-ranking official of the Prime Minister's Office. The position holder is usually an officer belonging to the Pakistan Administrative Service serving in BPS-22 grade. The Principal Secretary advises and assists the Prime Minister on all the official business routed through the PM Office, and because of this the PSPM is generally regarded as the most crucial aide to the Prime Minister. The current Principal Secretary to the Prime Minister is Muhammad Azam Khan.