Excellent find, nvubu. I'm watching it now.
At about 11:00, I noticed that as the Sunderland skipper increased power, the mixture controls moved automatically.
The Wikipedia page is worth reading:
https://en.wikipedia.org/wiki/Coastal_Command_(film)
The participants in the film were active RAF officers, NCOs and aircrew, and RN officers. The film featured pilot Roger Hunter and Flight Sergeant Charles Norman Lewis. On 25 August 1942, Lewis was killed on a flight that Prince George, Duke of Kent was undertaking as a morale-boosting mission to Iceland.