“It was not war, but it was certainly magnificent.” That was one officer’s description of the Christmas truce of 1914 in which British and German troops along many parts of the frontline briefly stopped killing each other and wished the enemy the compliments of the season. It was an extraordinary event, but also one that now comes wrapped in muddy layers of mythology.

In this centenary year, the truce is ubiquitous. Sainsbury’s made it the centrepiece of its Christmas ad campaign, following the narrative laid out by Paul McCartney in 1983 in the video for his hit single Pipes of Peace: sodden trenches; letter from home prompts moment of high emotion; two plucky soldiers on opposing sides forge an intense meeting in no man’s land; a game of football breaks out (lucky someone remembered to bring a ball); gifts are exchanged; artillery fire brings a hasty end to the festivities. Short, sharp, tear-jerking.

The McCartney take on history has hardened into orthodoxy, but the notion of a single meeting in no man’s land on Christmas Day culminating in a football match between Brits and Germans is false. “I can understand why the symbolism has emerged,” says Chris Baker, former chairman of the Western Front Association and author of a book on the truce. “It’s a positive, uplifting kind of view. But the reality is rather different.”

Fraternisation did not begin with the Germans singing Stille Nacht on Christmas Eve, as the symbolists – and Sainsbury’s – would have it. It started much earlier – Baker cites one example of soldiers from the second battalion of the Essex regiment meeting German troops in no man’s land on 11 December.

“Men’s curiosity was becoming an important factor in their day-to-day lives,” he says. “They could hear the other side. They could smell their cigarettes. They could occasionally glimpse them.” Trenches in this early phase of the war were rudimentary – Baker calls them “scratches in the ground” – and, in places, less than 100 yards apart. The two sets of troops were living in each other’s pockets.

The weather in December had been wet, but a cold snap began on 23 December and the ground froze. The snow-flecked portrayals of the truce are accurate. “You start getting men hearing soldiers across the other side of no man’s land singing and showing lights,” says Baker. “Men started singing back and passing messages across – putting a piece of paper in a tin can and throwing it. Finally, some men started leaving their trenches, waved on by the other side, and meeting in the middle.” A few would-be fraternisers were shot by snipers – not something you will see in the Sainsbury’s ad or at the Royal Shakespeare Company’s Christmas Truce show.

As for a game of football between the two sides, there is little hard evidence. “It comes down to one or two areas on the line where there are reports in men’s letters or things written very shortly after the event,” says Baker. “The most likely place is near the village of Messines [on the border between France and Belgium], where the first battalion of the Norfolk regiment played something with the 16th Bavarian reserve infantry regiment. There are two references to a game being played on the British side, but nothing from the Germans. If somebody one day found a letter from a German soldier who was in that area, then we would have something credible.”

A sculpture depicting a Christmas truce football match inside the remains of St Luke’s Church, Liverpool. Photograph: Paul Ellis/AFP/Getty Images

One of the shards of evidence comes from a much-quoted letter that appeared in the Manchester Guardian on New Year’s Eve 1914: “One officer met a Bavarian, smoked a cigarette, and had a talk with him about halfway between the lines. Then a few men fraternised in the same way, and really today peace has existed. Men have been talking together, and they had a football match with a bully beef tin, and one man went over and cut a German’s hair!”

A kickabout with an old tin which may or may not have involved Germans is, however, a far cry from the fully fledged game often imagined. Military specialist Taff Gillingham advised Sainsbury’s on its Christmas ad and lobbied hard to keep the kickabout in perspective. “Football played an insignificant role in the 1914 truce,” he tweeted recently. Not least, as Baker points out, because it would have been impossible to play any kind of organised game amid the barbed wire and bomb craters of no man’s land.

None of these historians’ caveats worry the football authorities. The Football Association coordinated events in schools and football clubs to commemorate the ceasefire; the Football Remembers project financed a memorial to the truce, unveiled last week at the National Memorial Arboretum in Staffordshire by the Duke of Cambridge; and teams from the British and German armies will recreate the famous “match” tonight in a centenary game at Aldershot Town’s stadium.

Uefa has also been keen to get in on the act, and last week Michel Platini, its president, unveiled a memorial to the truce and football’s role in it at Ploegsteert – known as Plug Street to British troops in 1914 – in Belgium. “I pay tribute to the soldiers who, 100 years ago, showed their humanity by playing football together, opening an important chapter in European unity and providing a lasting example to young people,” he declared. The Daily Telegraph reported last week that the Germans had won the game 3-2.

That happens to be the scoreline in Christmas Truce, the 1962 short story by Robert Graves, who served in the Royal Welch Fusiliers in the first world war and wrote Goodbye To All That. “We provided the football,” he wrote, “and set up stretchers as goalposts; and the Rev Jolly, our padre, acted as ref. They beat us 3-2, but the padre had showed a bit too much Christian charity – their outside-left shot the deciding goal, but he was miles offside and admitted it soon as the whistle went.” Graves’s fiction has been incorporated into fact.

The fraternisation almost immediately made headlines. “Since Christmas there has come over in the soldiers’ letters home from the trenches in Flanders the news of all those spontaneous little groups of truces which on Christmas Day and its Eve sprang up at intervals all the way down those trenches,” reported the Guardian in early January 1915. “It was the simple and unexamined impulse of human souls, drawn together in face of a common and desperate plight.”

An officer wrote in a letter quoted by the Guardian: “I found a large party of Germans and our people hob-nobbing together, although an armistice was strictly against our regulations. The men had taken it upon themselves. It was the strangest sight I have ever seen.”

In another letter cited in the paper, Corporal TB Watson writes: “We were all standing in the open for about two hours, waving to each other and shouting, and not one shot was fired from either side. This took place in the forenoon. After dinner we were firing and dodging as hard as ever; one could hardly believe that such a thing had taken place.”

Though the memories of that glorious, icy interlude stayed with the participants, the truce had no legacy. It was largely quiet on Boxing Day and in the run-up to New Year but, after that, it was back to bloody business as usual. “Some people on the left have written up the truce as a kind of revolutionary act on the part of the poor old tommy,” says Baker, “but nothing could be further from the truth. It wasn’t in any way organised or political, and as far as I can see there was no attempt to stretch it out or use it as a basis to question the war in general.”

There were brief truces in some areas in other years, but nothing on the scale of 1914. Attitudes hardened, the trenches became more systematic, the artillery more accurate, the generals less forgiving. How could soldiers, they reasoned, embrace one day and kill each other the next? As casualties mounted, memories of this pause in the slaughter receded from public consciousness, to be replaced by numb horror.

The truce was largely forgotten for the next 50 years. “It was not really on the radar right through to the 1960s,” says Baker. It took the 1963 stage show (and later film) Oh! What A Lovely War, with its extended sequence about the truce, to bring it back to public attention. With its message of peace and overturning of orders, it appealed to a counter-cultural generation remoulding notions of the war.

Stoke City and Arsenal players pay tribute to the Christmas truce during Football Remembers week. Photograph: Clive Mason/Getty Images

Since then, interest has spiralled. In 1984, Malcolm Brown and Shirley Seaton produced a highly regarded history of the truce and, in 2001, American historian Stanley Weintraub produced his own account, called Silent Night. These books became source material for the 2005 French film Joyeux Noël, which was adapted as an opera, also called Silent Night, in 2011. The final episode of the 1989 series Blackadder Goes Forth alludes to the truce and the inevitable football match, with Edmund Blackadder complaining about having had a goal disallowed for being offside – another echo of Graves?

After 50 years in which the truce was largely ignored, the pendulum has swung completely and, over the past few weeks, it has felt as if the truce mattered more than the war. We cluster round this beacon in the darkness. “And all that marvellous, festive day and night, / they came and went / the officers, the rank and file, / their fallen comrades side by side / beneath the makeshift crosses of midwinter graves ...” wrote Carol Ann Duffy in her 2011 collection The Christmas Truce. “The truce didn’t change anything,” says Baker. “The Great War went on. But it was a hopeful sign that men could behave differently.”