Codenamed ‘Upkeep’, the 4¼ tonne bouncing bomb was Bomber Command’s very own version of a skipping stone. Basically, when spun backwards on the bomb rack and released at exactly the right moment from the right altitude, it would bounce its way to the dam (thus going over the nets) and the combination of forward motion and backspin kept it against the dam wall as it sank to a depth of 30ft and exploded weakening the dam; it would probably be more accurately called a bouncing depth charge. Initial designs in February of 1943 called for a spherical bomb, 7½ft in diameter, but not enough high strength steel was available to make this feasible so Wallis redesigned the bomb with manufacturing in mind. The result was a rolled steel cylinder, covered in wood cladding giving the bomb the appearance of a beer barrel although the final design of the weapon didn’t include the wood. A wheel on one end of the weapon allowed it to be spun up to 500rpm prior to release and all bombs, prior to being loaded on the aircraft, were balanced so that when spinning at 500rpm, they didn’t shake themselves or the aircraft apart. The next issue was that of how to carry the thing – even the Lancaster, Bomber Command’s largest and most capable aircraft had to be subjected to a number of modifications to allow carriage.

Such modifications included removal of the bomb bay doors, the addition of suitable frames for carrying the bomb, a method of actually spinning the bomb, installation of a pair of lamps, strengthening of the fuselage and replacement of the standard Lancaster’s TR1196 radio equipment with TR1143 VHF equipment normally found in Fighter Command’s Spitfires and Hurricanes. The bombs were to be spun by the addition of a Ford V8 engine but this changed such that the hydraulic supply, which normally powered the mid-mounted gun turret that had been removed as part of a weight saving exercise, was used to power a hydraulic motor. Even with all the weight saved by removing fairly major bits, the modified Lancaster actually tipped the scales at about half a tonne more than a normal aircraft due to all the bits and bobs that needed to be added. One of the last modifications was to the throttle assembly to take account of the fact that a 617 Squadron Lancaster would be pretty much at the absolute maximum weight limit. Just by adjusting the throttle stops and length of the control rods, each Merlin offered up more boost than normal. The result was the Lancaster B.III (Special), which, as the name suggests, was simply a Lancaster B.III with all the necessary tweaks and adjustments and in case you were wondering, a B.III is basically a B.I but the Merlins were built by Packard, not Rolls-Royce.

Ignoring the fact that platforms do exist to take a 22,000lb payload to 40,000ft, to do this raid today wouldn’t be much in the way of a challenge thanks to GPS or even basic inertial navigation systems but this was 65 years ago and at night! When you also consider bombing accuracy was typically measured in miles (and even by 1944, being less than 1,000ft off target was rare), it’s beyond belief that the guys of 617 Squadron didn’t actually just navigate their way to the target, at night, but put a 9,250lb metal tube right up against their target’s walls when they got there. Skill and balls of steel don’t cover it and don’t do the squadron justice. However, rather than just technological genius in getting “Upkeep” built, tested and onto a Lancaster, the guy (no pun intended) in charge of the new 617 Squadron, one Wing Commander Guy Gibson, is undeniably one of the reasons why the Ruhr valley laid under several hundred million tonnes of water after both the Möhne and Eder dams were breached during the “Operation Chastise” raid. Sadly, of nineteen Lancasters that left Scampton between 9:30pm on the 16th and 12:15am on the 17th, eight never made it back. Of 133 men that left Scampton, 53 never came home although their ultimate sacrifice on the raid was not in vain – just two dams were breached yet the morale effect on both sides was huge. Britain, having been backed into a corner, saw it as “light at the end of the tunnel” yet Germany had been hit, and hit hard. So much so, the massive redeployment of people to repair and then further defend the dams took them from other vital places.

Sixty-five years later after the raid (and to the day too) the Battle of Britain Memorial Flight and 617 Squadron, obviously also celebrating a 65th anniversary, headed to Derbyshire’s Dark Park and Derwent Dam to commemorate this meritorious achievement. The Derwent reservoir, conveniently with a two-tower dam, was used by 617 Squadron aircrew for intensive low-level flight training rather than bouncing bomb trials but without this training, the bombs may as well have been nothing but a pipe dream. A short service led by Reverend Sqn Ldr John Ellis started at 10am on the western side of the dam where a memorial and museum exists. To conclude the service, the BBMF and 617 Squadron would take centre stage with a number of flypasts over the dam by the Lancaster, a pair of Tornado GR.4s, a Spitfire, a Hurricane and the Dakota. A similar event took place back in 1993 but back then, 85,000 people turned out and duly brought local traffic to its knees – this time around, passes were issued for car parking at Fairholmes and other, smaller, carparks on the single road from the A57 up to Derwent Dam. A sensible move indeed and it didn’t stop people parking up in and around Bamford and walking to the dam as there was no restrictions whatsoever on people other than those at the actual service. Unlike 1993 though, Sky and BBC were also there to broadcast live footage back to goodness knows how many people!

At almost exactly 10:30am, The Phantom of The Ruhr came into sight at just 100ft above the water – and what a truly superb and almost spine tingling sight it was. It was at this point that the sheer difficulty faced by 617 Squadron on 16th May 1943 became somewhat clearer… 60ft above the water in a moonlit valley, being shot at and having to get height, distance and airspeed within a margin of error that was somewhere between zero and none is nothing but pure bravery. Or maybe madness. If it wasn’t for the fact that most, if not all, people were pointing cameras at the Lancaster, I’m sure there would have been a standing ovation and for those with a link to the raids I’m sure a tear would have been shed. Just a few minutes later, the Lancaster headed back up the valley. Five minutes later and the Lancaster had turned round for another ‘dam run’… however, it was 617 Squadron’s turn to get involved as two GR.4s (one of which, coincidentally, was marked with KC-N, the code of Leonard Cheshire’s Lancaster when took over from Guy Gibson as OC 617 Squadron in September 1943) closely followed the Lancaster over the dam albeit at a somewhat greater speed. Their second and final run was certainly impressive as both GR4s had the wings back at the 67º position and were given it some serious what-for! All it needed for the “full-on” effect would have been for both jets to have been bristling with weapons and the burners lit and the two crews certainly did their squadron and its heritage proud. It should perhaps also be briefly noted that 617 Squadron were the first Tornado unit to use the Storm Shadow stand-off missile in combat.

Just a short while after 617 Squadron had done their best to scare the living daylights out of the unsuspecting, the BBMF once again took centre stage with their Spitfire PR.XIX (PS915) and Hurricane IIc (LF363). Both made a number of flypasts and even introduced what appeared to be a choreographed manoeuvre by breaking formation in opposite directions, climbing up the valley sides before turning back and once again forming up for a flypast. A valley with a large reservoir is a novel place for that kind of stuff but it was certainly impressive. Not to be left out, even the Dakota C.3 took part by making a number of flypasts over the dam and, like the Lancaster, Tornados, Spitfire and Hurricane before it; it looked stunning against the backdrop of fir trees. The last time the anniversary of Operation Chastise was celebrated on such a scale was fifteen years ago – let’s just hope it won’t be quite so long before it’s done like this again… such as 2013 for the 70th anniversary for instance.