Complex sentence: Burnett retired from the RAF shortly after his return to Britain, but in 1943 he worked full-time in the RAF's cadet organisation, the Air Training Corps, as the commandant of the ATC's Central Command.
Split into simpler sentences: Burnett retired from the RAF shortly after his return to Britain. However, in 1943 he worked full-time in the RAF's cadet organisation, the Air Training Corps, as the commandant of the ATC's Central Command.