How was They Shall Not Grow Old made? Peter Jackson reveals the extraordinary technology behind his First World War film

Within three months, the professional peacetime army had been all but wiped out. Their formidable musketry – 15 well-aimed rounds a minute meant that the enemy thought they were facing machine guns – had helped stop a swift German victory. They’d blown away the flower of German youth in the first battle of Ypres in 1914 (to this day it’s known there as the Kindermort, the slaughter of the innocents), but few of the “Old Contemptibles” themselves were left when it was over.

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William survived, though. He survived Gallipoli, too, and won a Distinguished Conduct Medal there. He was wounded on the first day of the Somme and recovered just in time to fight at Passchendaele. Against the odds, he survived the war. But it took its toll. He died at 50, broken by his wartime injuries; one more forgotten hero of the “war to end all wars” – forgotten if it wasn’t for the grandson he never met.

Peter Jackson, director and producer of blockbuster films like The Lord of the Rings trilogy, was raised on stories about his grandfather. “I grew up with the war in my household. Dad [who’d emigrated to New Zealand at the end of the Second World War] used to buy every book that came out about it, particularly those about places his father had been to. I read them cover to cover, and I’ve been fascinated ever since.”

He’s turned that fascination into the most extraordinary and moving tribute to his grandfather and the generation that fought and died in their hundreds of thousands in Flanders Fields. He’s used 21st-century technology to take us back a hundred years to see them as they saw themselves. Not flickering, jerky, anonymous victims of a war lost in history, but living, breathing young men, matter-of-fact amid all the mayhem, larky, even, on the edge of doom. We hold their gaze from beyond the grave and a century disappears. We are there.

I t wasn’t Jackson’s idea, but he leapt at it when the Imperial War Museum asked him to make a documentary to mark the centenary of the war’s ending. “They didn’t have any concept of it, other than wanting to use their archive, hundreds of hours of footage, in a different way.” Jackson turned to the special effects company he has in New Zealand. “I thought: how well can we restore it with the computer power we use for film visual effects today? We experimented and the results were far beyond anything I’d imagined.”

Jackson talks in military terms of “throwing a lot of firepower at it”. He was able to bring to bear the equivalent of 7,000 computers and 15,000 people to the threadbare footage. “I was amazed at how you can take shaky, jerky black-and-white film and make it look as though it was shot now.”

Jackson used techniques honed on his fantasy movies to sharpen the images and make them look crisp. But the crucial difference came when they started to work on the speeded-up jerkiness, the “Charlie Chaplin effect” as he calls it, of the old film. It was shot, often on hand-cranked cameras, at speeds between 13 and 15 frames a second. His team didn’t just slow the film down, they used computers to create artificial frames between the existing footage, making it 24 frames a second, smooth, modern and lifelike.

Restoring the black-and-white footage was the main job, he says. Colour and 3D “was the icing on the cake”. It was done carefully by hand, using the most advanced computer technology. “It feels like you’re watching the Gulf War,” he says. “We’ve tried to make it close to what you could shoot on a video camera or your iPhone.”

There was no sound on the original footage, but Jackson’s team have created a convincing soundscape that brings the film to life. You hear footsteps, tiles falling off a roof after a bombardment, as well as feel the shuddering impact of the shelling. They used lip readers to work out what the soldiers were saying and got actors to perform it “in a very real, natural way”

“The end result,” says Jackson, “is that we see that war the way they saw it.”

To match the resurrected pictures, Jackson has overlaid interviews from more than 120 surviving veterans that were recorded in the 1960s and 70s by the BBC and the Imperial War Museum. “They weren’t young then, but they weren’t ancient either,” he says, “and they were able to recount things incredibly well and talk with a great deal of honesty.”

The film starts with the original flickering black-and-white inset in the centre of the screen, the chattering of a projector, and the veterans cheerfully signing up to fight. “I’ve never been so excited in my life,” one says. “Such a relief from the boring jobs at home, you see,” says another. A lot were under age, 15 or 16.

We see them smoking and joking about ill-fitting uniforms, boots that they’d urinated on to soften the leather. We watch them brewing up tea from water that had boiled in the cooling sleeve of their machine guns.

When the action shifts to the front in Flanders, the mood darkens and, in a moment of filmic genius that brings a lump to your throat, the picture fills the screen, is suffused with colour, amplified with sound. In an instant, it’s real. We’re in the trenches with the rats and lice. The ground shudders with explosions. “They say your past comes up in front of your eyes,” a veteran says. “I was only 19. I hadn’t had any past.”

We see the soldiers in and out of the line, joking about queuing for the open-air lavatories and the everlasting bully beef and plum duff at one moment, quaking among the corpses under German bombardment the next. The film doesn’t blink when it comes to the horrors. Fly-blown corpses, a gangrenous foot, young flesh blown to pieces by high explosive. But nothing we see matches the veterans’ phlegmatic descriptions of what they saw.

And all the time these ghosts brought back to life make lingering eye contact. Human again. Like us, only much more stoical and with worse teeth. Their stoicism impressed Jackson most. “The thing that amazed me was their lack of self-pity. They didn’t feel sorry for themselves and the majority of them didn’t feel sorry they’d experienced it.”

War’s end seems as much an anti-climax as a relief. Most seemed to find it difficult to relate to those who hadn’t shared what they had been through. “We were a race apart,” said one.

Jackson thinks it will surprise those with our preconceptions of the First World War. “I didn’t want a modern spin on it. I wanted them simply to say it as they saw it.” At the end, the film reverts to flickering black-and-white as the war is symbolically returned to the past.

He’s left thinking about what happened to the men he’s cinematically brought back to life. “I wonder about these guys all the time. You see their characters and personalities; some make me smile and laugh. I always wonder if they survived or not. Hopefully, their descendants might now recognise them and come forward with their stories.”

The one thing this restoration does is make the faces of these men come alive

And the impact making the film has had on him? “I’ve been looking at documentaries and First World War films for as long as I can recall, and I’ve never seen anything that has affected me as much as what I’ve seen in the last year or so while we’ve been restoring this. Because the one thing this restoration does is make the faces of these men come alive.”

It is, as it’s intended to be, a brilliantly realised impression of what it was like to be a Tommy in the trenches, no more. It’s narrowly focused. Much of the war is not mentioned. There is no context, no cause or consequence. That, of course, is its strength.

Copies are being sent to every secondary school in the country. It will certainly promote empathy with that lost generation, but I wonder how much it will add to their understanding?

We’ve come to see the First World War as a pointless waste and our soldiers as sacrificial victims who gave their lives for nothing in a futile conflict. But that’s not how they saw it, most of them, anyway, including, I would guess, Sergeant William Jackson. All war is a tragic waste, but the Kaiser’s territorial ambitions were not that very different from Hitler’s, and if Germany had triumphed, Europe would be very different today. They did not die totally in vain.

We will remember them, and William’s grandson, with this haunting film, has made sure of it.

They Shall Not Grow Old will air on Sunday 11th November 2018 at 9.30pm on BBC2