Thanks Andy. It's actually a Spit PR19, painted as a MkXIV. From what I remember, for that season, the codes were the initials of a Group Cpt or WingCo, but I can't remember who! The 'Flight change the schemes / codes of all aircraft every couple of years, to avoid favouring any individual or squadron, and she's worn numerous 'disguises' since !
At the time, the Lanc, for example, was still wearing Guy Gibson's codes, AJ-G.