Original: Sir William '' Billy '' McMahon , GCMG , CH ( 23 February 1908 31 March 1988 ) was an Australian Liberal politician and the 20th Prime Minister of Australia Early life McMahon was born in Sydney , New South Wales , where his father was a lawyer .
Simplified: Sir William McMahon ( 23 February 1908 -- 31 March 1988 ) was the 20th Prime Minister of Australia .