//Are you sure it was a Lancaster and not a Wellington Bomber.
10 miles from Sheffield is Derwent Reservoir where the Dambusters practiced their bouncing bomb raid on the Ruhr Valley.//
It would be very unlikely to be a "Wimpy". First of all recognition - easy-peasy as the Lancaster has four engines and the Wellington two. Second, the dambusters flew Lancs not Wellingtons so if there was anything going on to do with "Operation Chastise" commemorations or re-enactments a Lancaster would be used. Last of all (and probably a clincher) is that there are no airworthy Wellingtons in the world. In fact there are only two complete survivors. One is at the Brooklands Museum in Surrey. It was recovered from the bottom of Loch Ness where it ditched in 1940 during a training flight. The other is in the Royal Air Force Museum at RAF Cosford. Neither is airworthy nor ever likely to be.