Prime Minister of New Zealand ministerial power; in 1912 Thomas Mackenzie was the last prime minister to lose power through an unsuccessful confidence motion in the House of Representatives. One change brought about by the First World War was direct participation in governing the British Empire. Previously, New Zealand prime ministers had attended occasional colonial and imperial conferences, but they otherwise communicated with London through the governor (a position then appointed by the British government). In 1917, however, British Prime Minister David Lloyd George offered the New Zealand prime minister a seat in the Imperial War Cabinet, the British Empire's wartime coordinating body. In 1919,
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