"K7211", the 29th production Whitley, served as the prototype for a further advanced variant of the aircraft, the "Whitley Mk III". The Whitley Mk III featured numerous improvements, such as the replacement of the manually operated nose turret with a powered Nash & Thompson turret and a powered retractable twin-gun ventral "dustbin" turret. The ventral turret was hydraulically-powered but proved to be hard to operate and added considerable drag, thus the Whitley Mk III was the only variant to feature this ventral turret arrangement. Other changes included increased dihedreal of the outer wing panels, superior navigational provisions, and the installation of new bomb racks. A total of 80 Whitley Mk III aircraft were manufactured.