Chastise: The Dambusters Story 1943. Max Hastings

Nant-y-Gro dam. On 10 May 1942 Wallis and his wife Molly travelled to Wales with Collins’s team to witness experiments on the full-sized dam. These established that if an explosion took place at any significant distance from its wall, the blast was too weak to precipitate a fracture. Collins wrote: ‘A solution to the problem was, however, found almost by chance shortly afterwards.’ His team needed to remove one of the damaged scale models at Harmondsworth, and used a contact charge to shift the concrete. The result was devastation, on a scale unmatched by any ‘near-miss’.

      Further tests confirmed the result, and on 16 July Wallis received an invitation to attend a full-scale demonstration a week later. He was nettled by the short notice, and warned a little pompously that he was working under such pressure – presumably on the Windsor bomber – that he would probably be unable to get away. Nonetheless, he was present at Nant-y-Gro when, on the 24th, army engineers blew a 279-lb charge of which the effects were filmed with high-speed cameras brought to North Wales from the Royal Aircraft Establishment at Farnborough. The test explosion proved a triumph, blasting a breach in a masonry construct that was, for practical purposes, a small-scale version of a German dam.

In the following month, Collins submitted a report which concluded that if a charge weighing around 7,500 lb was exploded at a depth of thirty feet against the wall of a dam such as the Möhne, it should be capable of achieving a breach. Such a weapon would not require the creation of a new bomber to carry it, but was within the lifting capabilities of the new Avro Lancaster, subject to appropriate modifications. Thus, suddenly, the most intractable obstacle to an attack on Germany’s masonry dams was removed: it seemed feasible – in theory at least – to convey to the target sufficient explosive to destroy it. Credit for the principal scientific achievements that made possible Operation Chastise should rightfully be shared between Collins, who resolved the challenge posed by the physics of destroying a vast man-made structure, and Wallis, who conceived a technique whereby the necessary charge might be laid from the air with the exactitude indispensable to success.

      In the late summer of 1942, a situation obtained wherein Barnes Wallis had devised a revolutionary weapon, of which the scientific principles were agreed by most of the experts who studied them to be sound. The Royal Navy was excited about its possibilities for use by the Fleet Air Arm. Widespread scepticism nonetheless persisted, shared by MAP’s David Pye and his deputy, Ben Lockspeiser, about whether the resources could be justified to pursue a speculative technology that could only be used over water, and which demanded superhuman courage and skill from aircrew who would have to launch it against an enemy. Moreover, every aircraft which carried such a bomb would require expensive modification.

Such reservations were fully justified. Lockspeiser wrote to Tizard on 16 June: ‘It is quite impractical and uneconomic to modify our bombers in large numbers for the special purpose of carrying any particular bomb.’ Nonetheless the Admiralty’s enthusiasm, and the uneasy acquiescence of MAP’s AVM Linnell, sufficed to secure a request for Vickers to fit a Wellington twin-engined bomber to carry a prototype Wallis bomb, of which on 22 July an order for twelve examples was placed with the Oxley Engineering Company. On 25 August Wallis attended a meeting at MAP at which arrangements were agreed for a series of trials to be conducted a month later, at Chesil Beach in Dorset.

      It is striking to notice, at this stage, two camps in the service ministries and the defence scientific community about the whole project. One faction believed that Wallis’s weapons were fanciful; would never work. The other cherished wildly over-optimistic fantasies concerning their war-winning potential. Fred Winterbotham wrote to the parliamentary secretary at the Ministry of Production on 14 September 1942, speculating about what Wallis’s bombs might achieve: ‘If this new weapon is intelligently used, e.g. for simultaneous attacks on all German capital ships and main hydro-electric power dams, there is little doubt but that Italy could be brought to a complete standstill and that industry in Germany would be so crippled as to have a decisive effect on the duration of the war … To attain this result much preparation and careful planning are clearly required and meanwhile I repeat nothing is being done.’ Here was a manifestation of a British yearning, characteristic of its time and place, for some dramatic stroke that might sidestep battlefield slaughter and bring the war to an early closure. Winterbotham’s note took no heed of the Alpine difficulties in the way of his fantasy, prominent among them that its fulfilment would require hundreds of bombers to be modified to carry Wallis’s weapons. Meanwhile its expectations about what these, or for that matter any, bombs might do to the Axis drifted into fairyland.

That autumn of 1942, the bomb project languished. Oxley Engineering experienced difficulties in constructing the test weapons, and in October Wallis was kept at home for several days by illness. Only on 2 December did he at last board a modified Wellington, piloted by veteran test pilot Mutt Summers – the very same who had parachuted more than a decade earlier from one of the engineer’s less successful prototypes – for a trial of the backspin technology. It worked, though no test bombs were dropped.

      Two days later, on the afternoon of the 4th, the Wellington took off for Dorset, where on Chesil Beach a camera crew waited to record the trial bomb-dropping. The first two tests, with non-explosive fillings, resulted in the spheres bursting on impact. When a subsequent succession of droppings took place, Wallis watched from the shore. Outcomes suggested that the technologies for releasing the bomb from an aircraft, and for its subsequent bouncing progress, were viable. Yet repeated collisions with the sea at speeds of over 200 mph imposed enormous stresses on the projectile during its bouncing progress. Half-sized prototypes disintegrated. Their begetter undertook modifications and adaptations, still convinced that the principles of his creation – or rather, his instrument of destruction – were sound.

      Following these further developments, Wednesday, 20 January 1943 found Wallis ensconced in Weymouth’s Gloucester Hotel, from which he wrote to Molly: ‘I do wish you could come & share this lovely room. It would be just perfect with you here. If you could come tomorrow by the mid-day train, do … Now we are scheduled to start [tests] at 10 a.m. … so I must go to bed. All my love little sweetheart, and come if you can …’

She came. Almost two decades of marriage had done nothing to cool the couple’s passionate romance. Molly, still only thirty-seven, was now responsible for six children, including a niece and nephew whose parents had been killed in the blitz. This brood was surrendered to their nanny while she set forth for Dorset. On 24 January she wrote to the children from Weymouth about her visit to their father:

      … A lovely time it’s been. This morning I drove out with him and the others to the nearest point I was allowed [to the bomb tests] & then I got out and walked back. 8 miles of lovely road, high up with the Downs one side & the sea to other. It was sunny & clear. I did enjoy it. Of course it’s quite mad that they shouldn’t let me watch the proceedings seeing as I’ve lived with it since last February & probably know more about it than anyone save Barnes. But it’s quite true – policemen do bob up and turn you away. I suppose the others would say ‘If that wife why not my wife’ little knowing what a very special wife this one is.

      Darling Barnes. You should see him among these admirals and air vice marshals patiently explaining and describing to them & they drinking it all in – or trying to. And he’s so quiet and un-assuming none of them could imagine what pain & labour it’s been. How he’s got up in the middle of the night to go up to the study & work summat out. No wonder he looks drawn and tired. I suppose if he were a self-advertiser he’d have been Sir Barnes in the New Year Honours. Oh well, it’d have been a nuisance. But it’s an exciting life & no mistake.

The contrast seems extraordinarily moving between the private domesticity and indeed passion within the Wallis family, and the devastating public purposes which its principal was pursuing. Some might find it repugnant, in the light of what later befell Upkeep’s victims, but it must never be forgotten that Barnes Wallis’s country was engaged in a war of national survival against one of history’s most evil forces. The engineer was straining every sinew, and all his own astonishing gifts, to assist the Allied cause. During that 24 January trial in Dorset which Molly Barnes was not permitted to witness, one dummy bomb achieved thirteen bounces. Next day, another managed twenty. Wooden test