In 1942, Jeffrey was posted to the South West Pacific, where he helped organise No. 75 Squadron for the defence of Port Moresby, and No. 76 Squadron prior to the Battle of Milne Bay. He served two stints in charge of No. 2 Operational Training Unit in southern Australia before the end of the war, broken by command of No. 1 (Fighter) Wing in the Northern Territory and Western Australia during 1943–44, at which time he was promoted to temporary group captain. Jeffrey was transferred to the RAAF reserve after the war but returned to the PAF in 1951, holding training posts in Victoria and command of RAAF Base Edinburgh in South Australia, before resigning in 1956. Outside the military, he was a grazier and stockbroker. He died in 1997 at the age of 83.