Although 7,377 Lancaster aircraft were produced between 1941 and 1946, only two remain airworthy. One (a Mk 1 nicknamed ?Thumper?) is maintained by the RAF?s Battle of Britain Memorial Flight (BBMF), and the other by the Canadian Warplane Heritage Museum (CWHM). Here they were photographed as they flew through the iconic Derwent Valley. The derwent Valley was used to practise the bomb run on the German dams.