Danny, I think that picture shows the UK's brief dalliance with the barbette, as compared to a manned turret. Both mid upper and ventral were controlled from the glazed position shown at the rear of the a/c. Brief, as:-
The prototype barbettes were completed and despatched to RAE Farnborough in early 1944, where they were fitted to Lancaster (LL780G). Some trials took place, but it was thought that hostilities would probably be ended by the time the system was ready for operational use, and the project was terminated in autumn 1944.
They both packed twin 20mm Hispano Cannon which would have made someone's eyes water! Perhaps their use by Tiger Force would have been compromised by the weight, and hence range, implications for operations in the Far East.
