Reading from an entry on HMS Fiji's history it says;
'Before she could join the taskforce, at 18.00 hours on 1 Sep, 1940, U-32 attacked the Dakar Task Force (Operation Menace) about 40 miles north-northeast of Rockall and reported a hit with its last torpedo on the troop transport Scythia, but in fact HMS Fiji (58) (Capt W.G. Benn, RN) was damaged and managed to return under own power to the Clyde, arriving on the evening of 3 September.
Five ratings were killed.
The cruiser was repaired at Greenock for six months.
She was fitted with radar and her Anti-Aircraft armament was also marginally increased.'
but no information as to what AA armament was added.
Narrowing down the possibilties it could have had added a single barrelled pom pom in the photo which was obviously an army modification.
Joe