Lockheed Ventura four gun turret

[Larry]

I was watching Pathe News films on line and saw that in one film concerning Ventura Ops of 2 Group RAF in the UK, that a few Venturas one of which was carrying SB codes of 464 Sqn RAAF, had turrets equipped with four 0.303 machine guns, in a smaller profiled dorsal turret nothing like the original Boulton-Paul domed type seen on Lockheed Hudsons and early Venturas, nor was it the Martin turret with two 0.50 Browning MGs.

According to my references the Mk I had the BP domed turret and P&W R-1850 engines, the Mk II had the same armament but P&W R-2000 engines. The Mk IIA had the dorsal turret from Martin and so did the Mk GR V. So which Mk used the four gun turret and why no mention of it in books covering 'RAF' use of Venturas in 2 Group aircraft?


NB - Ignore reference to 21 Sqn in the last photo - that's my error.