Excellent programme were it not for some of the 'stock shots' used which appeared to have emanated from across the pond where as far as I'm aware, the ATA never operated ('cos they had their own ferry service).
I too wondered about the aircraft with two sets of exhausts but it was so late at night and the shot was stretched to fit a 16/9 picture so I never twigged it was a Battle!
Never heard of that engine before, presumably its development was overtaken by turboprops.