John Duffield went to Papua New Guinea as a cadet Patrol Officer in 1962 when he was 18 years old. His first posting was to the Central District where he was posted to Tapini, Woitape and Port Moresby. In 1964 he went to Manus District and spent his time at Tulu Base Camp and Lorengau. He became a Patrol Officer and a Magistrate for Native Matters. After Manus, he was posted in 1966 to Ioma Patrol Post in the Northern District and after leave in mid 1968, John was posted to Lorengau and Kokoda and became an Assistant District Officer. He was then posted to Tufi where he was made acting Assistant District Commissioner. After leaving Tufi in January 1970, John became a Political Education Officer and his work in Papua New Guinea from then on involved preparing the country for Self Government and Independence. In 1971 he married his wife Rowena, who was a teacher in Lorengau, and the two were transferred to the Southern Highlands District in 1972 where he became a District Government Liaison Officer. In the Southern Highlands he worked with groups of people conducting seminars and courses about Self Government and the work of the Constitutional Planning Committee, and he was away from his family for at least half of his time. In 1974 he and Rowena were posted to the Gulf District and John's major programs were Independence, The Purari Project and Provincial Government. John was the Executive Officer for the Gulf Independence Day Committee.

John and Rowena Duffield left an Independent Papua New Guinea in June 1976.

John Duffield became the acting Assistant District Commissioner for the Tufi Sub-District from 1969 to early 1970. By this time his role was broadening to include community development, community education and training. In January 1970 he took up duties as a District Political Education Officer for the Northern District, which involved carrying out political education courses for councillors, village leaders, high school students, Christian missions, social workers and public servants. He was transferred to the Southern Highlands District in February 1972 as the District Government Liaison Officer, a role responsible for setting up a consultative network for advising the Constitutional Planning Committee. Before leaving Papua New Guinea in 1976 he was the Executive Officer for the Districts Independence celebrations.

Rowena Duffield, John’s wife, trained as a teacher at ASOPA in 1968/69 and conducted adult education classes in Mendi Town.