Malta - Belfast 1943 Mystery

[Frank Schofield]

A cover sent from Malta in August 1943, addressed to Belfast, from a Naval Officer, partial details on the reverse, (his name covered by brown GPO tape), Paymaster Lieut. RNVR, Coastal Forces Base, Malta.
Cancelled by a large mute circular POST OFFICE / MARITIME MAIL, no tombstone censor visible, but sealed with a tape OPENED BY / EXAMINER AC 8, this unlisted by CCSG?, my first thoughts were AC = Admiralty Censor, but I am told by Nick Colley a similar tape with the initials AG is known. At the bottom left, covered by the tape there appears to be two names, only 20/8 and RNVR are showing. The censorship may have been much tighter at that time because the date 20/8 was just before the invasion of mainland Italy on 3rd September 1943.
Upon arrival in Belfast it has been intercepted and opened, then resealed by brown GPO tape, with three strikes of the single ring CENSOR OFFICE / 6 SP / 43 / BELFAST (one on the front, two on the reverse, apparently only 4 recordings of this scarce strike are known)
Why was the Censor Office interested? It has been suggested that the addressee or the address were on a Security Service watch list, which seems a possible answer.
Any comments appreciated.
Frank Schofield