Sadleir joined the Australian
Department of External Affairs in 1958. He was an advisor to the Australian delegations to the
Inter-Parliamentary Union, and was posted in Tokyo and Washington DC as Assistant Secretary of the department's North Asia branch. From 1977 to 1981, he was Deputy Director-General of the
Office of National Assessments, an intelligence agency reporting to the Prime Minister of Australia, under Director-General
Robert Furlonger. He was a
Permanent Representative to the United Nations and other international organisations in Geneva from 1981 to 1984. ==Consultancy career==