 Complete the following phrase:  Stirrup started his military career at the RAF College Cranwell in Lincolnshire on 1 April 1968 and it was from Cranwell that he received his commission on 31 July 1970. He was promoted to flying officer on 31 July 1971 with seniority backdated to 31 January, and to flight lieutet from 31 July 1973. From 1973 to 1975, Stirrup was on loan service with the Sultan of Omans Air Force. While in Oman Stirrup flew BAC Strikemasters during the 