The centenary of the Armistice is given a cinematic commemoration that brings the past vividly to life in They Shall Not Grow Old. Not only so, director Peter Jackson – he of Lord of the Rings, The Hobbit and King Kong - uses his technological savvy and his familial connection to the conflict to conjure a portal to the past that could well unlock archive footage for generations to come.

It was a bold move for the Imperial War Museum to throw open their vast store of silent, black and white film and ask Jackson to come up with a fitting way to mark the 1918-2018 centenary. Bolder was the Kiwi director’s insightful decision not to put a contemporary spin on old material, but to bring the men who marched away brilliantly back to life. Everyone’s seen it – the jittery, fast-walking, black and white footage; the silent film-stock flickering; the images of our forefathers in a conflict that’s now an era away, wars ago.

It’s distant, redolent of a foregone age locked away by hindsight and history syllabuses. And so it is for the first 15 minutes of this eye-opening film. Boxy black and white footage plays out as veterans – recorded in the 1960s and 70s – tell of the fun, hope and exhilaration of joining up; even of being given a white-feather when seen in civvies. The train journeys, the arrival in the foreign fields and the jaunty introduction to the land of duckboards, trenches and booming horizons. And then…

Suddenly the cinema-screen opens like a window. And the men are here and now, in full colour, seen and heard like the sons, brothers, uncles and dads they were. Laughing, joking, going to the loo over a laid-out pole, learning the drill, acting the goat, their words heard for the first time since they came out of their mouths. Not so much Lord of the Rings, it’s a Narnia-like experience, the past stepping into the present. The movements are nimble, fluid; the toothy grins are real and in need of a dentist; the fabric is rough, the mud is wet. Jackson unlocks the footage.

Computers fill in the frames, giving the film stock a flow. Incredible attention to detail went into the colourisation: flesh tones, eyes, mud, uniform; even, in several awesome moments, the specks of debris in huge explosions; and the roof tiles slinking off a farm-house with every reverberation from a field gun. Jackson employed forensic lipreaders to extract the lads’ words from the footage, re-voiced by actors in the dialect of the regiment. The result is vivid, eerie and electrifying – which is exactly the point.

They Shall Not Grow Old tells us nothing new, the veterans’ voices have been heard before, some in the landmark 1964 TV series The Great War. But Jackson’s coup, and his gift to us in this centenary year, is to free us from our cultural prisms. Theatre and cinema have played their part in our perceptions: everything from the History Channel to All Quiet on the Western Front, from Journey’s End to Oh! What a Lovely War, from Blackadder Goes Forth to The Wipers Times. Most have sought to humanise the men, even if the ‘war is terrible’ trope understandably hangs round them all. Surprising then to hear the veterans say they’d have done it again.

To hear their humour, see them playfully knocking each other’s hats off, see the captured Germans sharing a smile and a cigarette as they help to carry the wounded. Most of the boys have clearly never seen a film camera, standing still as if for a photo but unable to keep their faces straight. Fittingly, Jackson reintroduces us to these people just as our living connections have disappeared. And maybe he’s shown the way for other filmmakers to bring to life the men, women and children still caught in archival black and white.