"HA" is 649 (Dursley) Squadron from what I have found online. Apparently the Squadron was never officially formed so I have no idea why an aircraft would bear those markings. The only supposition I could offer is that the aircraft did not bear "HA" as a squadron identifier but that it belonged to a pilot of rank sufficient (Probably Wing Commander or higher) to have their initials painted in lieu of normal markings.
It could also have been a Headquarters unit which would imply that the aircraft was used by Air Staff.
Addendum: The Squadron operates as an ATC (Cadets) unit in the modern age.
Last edited by Ace_Pilto; 10/12/18 09:28 AM.