A genealogist was astounded to discover letters sent home from the First World War trenches by her great uncle describing the unofficial Christmas Day truce – which she had thought was the stuff of legend.

Oswald Tilley was just 19 when he penned the note home to his parents in Kingsland Road, Haggerston, telling them that the truce between English and German soldiers was the “most practical demonstration” he had ever seen of “peace on earth and goodwill towards men”.

“Just you think that while you were eating your turkey etc, I was out talking and shaking hands with the very men I had been trying to kill a few hours before!! It was astounding!” he writes.

Although the rest of his family were pacifists, Oswald signed up at the beginning of the First World War, went to France and was killed four months later in April 1915.

During the short time he was in the London Rifle Brigade, Oswald sent many letters home, most of which his great niece Cherrill Theobald had no idea existed until they were referenced in a book she was reading for research.

They are now kept in the Imperial War Museum, where she was able to read them.

In the letter about the truce he writes: “On Christmas morning as we had practically ceased firing at them, one of them started beckoning to us, so one of our Tommies went out in front of our trenches and met him halfway amidst cheering.

“They arranged for one of our officers to meet one of theirs and they arranged an unofficial armistice so that each side could bury the dead which lay between the trenches. After a bit, a few of our chaps went out to meet theirs until literally hundreds of each side were out in ‘No man’s land’ shaking hands and exchanging cigarettes, chocolate and tobacco etc.

“Our fellows brought in five dead Germans to them and we had a joint burial service between the trenches. The German officer thanked ‘you English friends’ for bringing them across.

“I had a chat with a German who used to work at Buchanan’s in Holborn!! Naturally he spoke English well and said he was tired of this job and said he did not think the war would last very much longer.”

Cherrill, a researcher at probate company Anglia Research, couldn’t believe it when she saw her great-uncle had been part of the Christmas truce. She said: “It’s like a legend, and there was he writing about it, that they came out into no man’s land and exchanged gifts.

“Oswald doesn’t talk about playing football but they definitely exchanged cigarettes and momentos, pencils, little tiny things, buttons, and he was part of that – it’s just extraordinary. The Christmases after that during the war this kind of thing was frowned on, and it was an off-the-cuff idea of these few brigades to do this. It didn’t happen all the way along the line.”

She continued: “They all thought the war was about to end, and they all said it would be over by Christmas and they were all still there. I don’t think they realised the seriousness and that it would go on for many years. It’s so sad that he was a young man and he was killed the following April. Whether that was a good thing that he didn’t have to fight another four years I don’t know.

“He was wounded in the back of his head and they tried to look after him as best they could in the trenches and he was sent to a medial centre by Boulogne and that’s where he died.”

Oswald, one of 11 siblings, had gone to war just as his mother had given birth to her last baby. After Oswald was killed, his sister Mabel gathered all his papers into a large scrapbook which includes pencil-written letters and drawings, letters of condolence to his parents, postcards, photographs and his metal tag.

“It’s not unusual that his sister had made a scrapbook,” said Cherrill. “This was usual if they lost someone in the war to collect their things together.”

Oswald is buried in a Commonwealth War Graves cemetery near Boulogne.