I think your relative's WOP/AG title may have applied to other aircraft as the radio gear was beside the navigator? The turret was power operated with single .303 Browning replacing the early Vickers. It appears to have had a tubular framework mounted to rotate with the turret and carrying the seat with a footrest; from ancient memories I think the Lancaster mid-upper had a similar arrangement. From the drawing you might think the gunner stood up to operate but the Blenheim was incredibly cramped to reduce frontal area and gain speed and the gunner's head and shoulders would have been up in the canopy.
Many years ago my ex-Army relative Jim was compiling a club history booklet and asked me to check over the memories of an ex-RAF navigator. He had never recounted this before and told Jim it had awakened old memories which he found unsettling but cathartic. He died a few weeks later.
As I remember his story, two aircraft, all that were left of his Blenheim squadron, were on the way to attack the invading Germans but nobody knew where these forces were. He tried to obtain latest info but the radio wouldn't work 'as usual, it never did'. Beneath the navigator was a second machine-gun firing aft and sighted through a mirror. He was wondering how anyone let alone himself could possibly hit anything with 'this wretched device' when there was a terrific crash and the port engine caught fire, closely followed by the starboard. They were being attacked by Me109s.
The pilot gave the order to bale out, he and the gunner escaping via roof hatches. The navigator pulled a lever and his seat, his table and 'that wretched machinegun' all fell out through an opening in the floor. All three crew landed with minor injuries and were sheltered by Greek communists but after a few days were betrayed by Government sympathisers and spent the rest of the war in captivity. He was one of seven survivors from 58 of his comrades who had gone to war. Hope this helps, sorry I can't remember any more.
Last edited by Geriaviator; 10th Nov 2020 at 17:06.