Whilst attending my ATC summer camp at RAF Bruggen (July 1972) I was able to inspect a former 16 Sqn Canberra B(I)8 recently retired to decoy duties.
The aircraft was complete, even down to its ventral gun pack. I was however surprised that the weapons bay had only a single pylon and a loom of wiring for the PALs (Permissible Action Links) associated with the carriage and delivery of nuclear weapons. There was no other option to carry conventional weapons.
I was rather perplexed as to why if the aircraft was going on a nuclear delivery sortie, that they would bother with the gun pack. It rather stretches the imagination that after having delivered their bucket of instant sunshine that anyone could be interested in shooting up targets of opportunity with a battery of cannon?