David,
unfortunately the radio is way out of my league and not to mention I still don't know exactly what was used in them.
David, your absolutely right, he would have been a very busy boy. The gearbox it located at about 10:00 in the turret and I don't know how the gunner could traverse, sight and shoot at the same time. He could only shoot one gun at once and he would have to lean over quite a bit to fire the 1/2" Vickers and get up very close and personal with the commander. As per your previous comment that it certainly does give you a different perspective what these chaps had to endure.
As Adrian said the brake is only release once the grip is squeezed. I can see that the grip is connected directly to the small pinion gear which is about 7:1 ratio and one turn gives 3 deg of turret rotation. It will be very easy to turn.