Quirk was born at his family's farm, Lambfell, near Kirk Michael on the Isle of Man, where his family farmed, the son of Thomas and Amy Randolph Quirk. He attended Douglas High School for Boys on the island and then went to University College London (UCL) to read English (the department relocated to Aberystwyth due to the war) under A.H. Smith. His studies began in 1939 but were interrupted in 1940 by five years of service in Bomber Command of the RAF, where he rose to the rank of squadron leader.