In 1942, the two-stage Merlin 60 aero engine became available for reconnaissance aircraft. The first 15 Spitfires with the new engine were conversions of standard Mk IXs made by the workshops of 1 PRU at RAF Heston. One of the best known operations undertaken by the Mk IX conversion was to provide photographs of the four dams slated to be destroyed by Operation Chastise; a PR Mk IX flown by Flg. Off. F. D. Fray brought back a famous series of photos showing the Moehne and Eder dams the morning after the raid.