Newly released photographs show how a team of World War II experts disrupted Nazi plans to bombard Britain – with the help of 3D glasses like those in modern cinemas.
Hitler’s deadly V-1 and V-2 rockets were early but effective weapons of mass destruction – unmanned flying bombs which brought terror to southern England.
But their impact could have been all the more devastating – costing thousands more lives, lengthening the war and threatening the D-Day landings – were it not for the fact that British intelligence worked in three, rather than two, dimensions.
One of the Royal Air Force’s most significant successes came with Operation Crossbow, when it tracked down, identified and destroyed many of the V-weapons which could have prolonged the war.
It did so by meticulously photographing the landscape of occupied Europe in a way that allowed officers to study every contour.
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Operation Crossbow is broadcast at 2100 BST on Sunday 15 May, BBC Two
Or catch up afterwards via iPlayer
BBC History: RAF Medmenham
BBC History: V-Weapons
Now the pictures have been brought to life using computer graphics in a BBC documentary thanks to research by the Royal Commission on the Ancient and Historical Monuments of Scotland.
During the war, the images were painstakingly analysed by a team of photographic interpreters – known as PIs – at RAF Medmenham in Buckinghamshire.
Their secret weapon was a stereoscope – a simple Victorian invention which brought the enemy landscape into 3D.
Working on the same principles as modern-day 3D glasses, it allowed the PIs to measure height, especially of unidentified new structures – such as rockets and their launch sites.
This technique was to prove decisive, and it saved thousands from the V-rocket barrage.
The Spitfire is well-known for the
role it played in the Battle of Britain, but less celebrated is its contribution to this crucial phase of the conflict.
A preview of Operation Crossbow, a documentary looking at how Hitler was defeated with the aid of 3D imagery
Pilots from the Photographic Reconnaissance unit, created in 1940, risked their lives by flying unarmed over Europe to take tens of millions of photographs, generating 36 million prints.
To make the 3D effect work, images had to be captured in carefully-plotted sequences which would overlap each other by 60% so everything would stand up when viewed through the stereoscope.
It made the job of the pilots – who, in addition, had to avoid enemy fire – an especially skilled and arduous one. Flying at 30,000ft, they were unarmed because of the weight of the five cameras carried on each Spitfire.
But it is a role of which 88-year-old Jimmy Taylor, a former reconnaissance pilot and the only survivor from the squadron, remains immensely proud.
“It was the best job in the RAF,” he says. “We flew the most beautiful aeroplane, the fastest of its day.
“We had no guns, no bullets, so I didn’t kill anyone. Physically, there’s nothing left of the air fights, nothing left of the bombing – but the photographs are still with us, and they’re still useful.”
Arguably, the squadron’s crowning moment came with Operation Crossbow.
It began in 1942, when a Spitfire flying over Peenemunde in north-eastern Germany spotted an airfield with three concrete-and-earth circles.
Initially, PIs studying the photos thought nothing of them.
In fact, Peenemunde was a vast research centre developing the V-rockets which the Nazis believed would win them the war.