Peter Jackson's new documentary isn't perfect, but it's implications are immense

The release of They Shall Not Grow Old is almost a historic event in itself. Using computer techniques from his feature films such as The Lord of the Rings, Jackson has transformed the original, scratchy, jerky, black-and-white silent film of a century ago into full 3D colour.

Little details, like the curl of cigarette smoke, the buzzing of flies or a shy grin, as Jackson has said, help to "pull these men into the modern world, so they can regain their humanity once more."

Instead of a narrator, They Shall Not Grow Old uses the voices of Western Front veterans, now long dead, taken from recordings preserved - along with the World War I film footage Jackson relied on - at the Imperial War Museum in London. Lip-syncing by actors is used, sparingly, to make the words of the soldiers on screen come alive.

Some historians have objected that in They Shall Not Grow Old, Jackson has defaced or falsified evidence. They have a point, in terms of the film's authenticity. Jackson is using his best guesses about how green the grass was, the exact blue of the sky, the colour of the soldiers' hair and eyes and tobacco-stained teeth.

What they said is not verifiable fact; Jackson worked with lip-readers for the words and made assumptions about the soldiers' accents based on where their units originated.

The documentary's title is itself a misquotation of a line from For the Fallen, Laurence Binyon's famous poem of 1914 ("They shall grow not old, as we that left grow old").

Although the colourized film and veterans' voices give it an air of verisimilitude, They Shall Not Grow Old should perhaps have opened with the common film disclaimer, "Based on a true story."

Despite those drawbacks, my own strong support for They Shall Not Grow Old comes from working with the original films all my professional life. Forty years ago, I catalogued the hundreds of hours of Imperial War Museum film from which They Shall Not Grow Old is constructed, and I have participated in the production of television history programs related to the war ever since.

They Shall Not Grow Old is only the latest, and by far the best, of many experiments (which began while World War I was still being fought) in film speeds and in the use of sound and colourization.

The implications for the future of historical documentaries are immense. It represents a proof of concept, showing what can be done with today's technology. If the same thing, or perhaps a less advanced and expensive variant, could be done within the budget of the average television documentary, a treasure trove of early silent factual films could be retrieved for modern audiences.

One disappointment is that the film's end credits do not include the cameramen who shot the original footage, led by Lt JB "Mac" McDowell, who was decorated for bravery.

Structurally and stylistically, They Shall Not Grow Old is indebted to these men, notably their 1916 film Battle of the Somme, arguably the world's first war documentary, which broke box-office records on its release.

Filming the Western Front was beset by the technical problems of a century ago, including hand-cranked cameras that could not be taken forward into combat. The inability to capture battle scenes and acts of heroism thus also limits the scope of They Shall Not Grow Old.

Another of my concerns about They Shall Not Grow Old is more important, because history is the story that we tell ourselves about who we are. Jackson acknowledges that the film reflects his personal view of the war, and he has selected and edited his material accordingly, emphasizing the ordinary soldier's experience.

What is most missed is the bigger picture. The Western Front of the documentary is unchanging and eternal; the war ends for no apparent reason.

In fact, plenty of film exists of the joyful liberation of northern France and Belgium in the last great Allied victories of 1918, in which U.S. troops played a critical part, but it is entirely missing from They Shall Not Grow Old.

That is a disservice to the old veterans who at the end of Jackson's film reflect that they are no longer sure what their war was about. They were entitled to have their achievement in winning it recognized.

Even so, if They Shall Not Grow Old leads even some of its audience to seek out the real history of the Western Front, that will be a bonus for what is a truly wonderful film and a lasting contribution to the continuing cultural exploration of World War I.