When I was a small boy in the 1950s, I often used to run around with my arms out wide whilst humming the theme from the Dambusters film, which chronicled the dramatic raid on the Ruhr Damns by 617 Squadron in 1943. The Derwent Reservoir was extensively used during the production of the 1955 film, probably because of its resemblance to the Eder and Moehne dams. A plaque at the dam’s west gateway and a museum in the west tower commemorate the role of the reservoir in this famous raid. The plaque states: “Derwent Dam was chosen because of its close resemblance to the German dams for intensive low level practice and bomb aiming techniques”.

It is a terrific story, but how important was the Derwent Valley in the preparation for the raid? Brian Robinson casts doubt on its significance in his chapter “Drowning Some Legends of the Upper Derwent Valley” in Scarthin Book’s “The Seven Blunders of the Peak”, published in 1994. His writing inspired my own interest and research. I can now offer the true story of the role of the Upper Derwent Valley in the Dambusters raid.

The importance of the Ruhr dams to German industry was realised as early as 1938 by the RAF’s Aerial Intelligence branch and, in 1941, Barnes Wallis suggested attacking Germany’s industrial heart by destroying the Ruhr dams using specially developed bombs. After a series of experiments, including practical trials on a dam at the Nant-y-Gro dam in the Elan Valley in Wales, he developed the concept of the “bouncing bomb”. On 26 February 1943, authority was given to proceed with an attack in May 1943, when it was expected that the reservoirs would be full following the spring rains. The operation was code named Chastise and Squadron X was formed on 17 March 1943 using specially selected crews; re-named 617 Squadron, it began training on 31 March for its secret mission. The crews were not told the targets but trained extensively on low flying at night, using the Wainfleet ranges in the Wash, whilst practice with the “bouncing bombs” took place of the Kent coast. As a cover story, the crews were told that they were training to attack the German warship the Tirpitz. Ironically, the Squadron was to attack and sink this ship in 1944. The crews were only told of the actual targets on the day before the raid.

Specific training areas were allocated 10 days before the raid: Eyebrook Reservoir, near Uppingham, for the crews due to attack the Eder dams; Abberton reservoir, near Colchester, for the raid on the Moehne Dam; and the Derwent reservoir for the crews who were to raid the Sorpe dam; reserve crews trained over the Wash.

There is evidence that the Squadron Commander, Wing Commander Guy Gibson, used the Derwent reservoir on two other occasions. 0n 28 March 1943, he flew a Lancaster over the reservoir to test his ability to fly over water at 150 feet in an area surrounded by hills. Later in April, he probably used the two towers on the Derwent dam to test the wooded bombsight being developed for the raids on the Eder and Moehne dams.

The Sorpe Dam differed from the other two targets in that it was not a masonry dam with pairs of towers but had a concrete core covered by banks of earth. As a result, it was attacked along its length rather than at right angles. On the night of 16/17 May 1943, 19 aircraft set off to attack the dams; five Lancasters had the Sorpe Dam as their primary target. Only two reached this dam and, despite the best efforts of the crews, it remained intact. The other two dams were breached causing severe flooding in the Ruhr valley and the loss of around 1,200 lives; sadly, about half were forced labourers from Eastern Europe. Eleven factories were destroyed, 114 seriously damaged and 25 bridges damaged. However, full water output from the dams was restored by 27 June 1943.

The major impact of the raid was probably the transfer of 20,000 labourers from their work on the Atlantic Wall to repair the dams, and the diversion of 10,000 troops to protect them from further attacks. Out of the 19 aircraft that took part in the mission, 11 returned. In all, 53 aircrew were killed and three taken prisoner, with 77 returning safely. The 617 Squadron continued to undertake specialist raids throughout the rest of the war, and the Squadron remains in RAF service to this day, now operating the Tornado GR4.

So the next time you walk alongside the reservoirs in the Upper Derwent Valley, you can astound your companions with knowledgeable comments on the true role of the Derwent Dam in 1943, when an elite group of RAF airmen trained for a legendary mission.

Geof Cole