First in the Field (2011) Hardcover Book - (651 Squadron Army Air Corps)

651 was the first Air Observation Post (AOP) Squadron, formed at Old Sarum on August 1 1941 to work closely with army units in artillery spotting and liaison. It was still part of the RAF but all the pilots, drivers and signalers were from the Royal Artillery, while the RAF supplied the Adjutant, Engineer Officer and technicians. It is therefore the premier Army Air Corps squadron.