He was the hero from a small Norfolk village who survived an infamous Nazi massacre, carried an injured friend to safety and, after five years as a prisoner, helped to bring the perpetrator to justice.
And now, more than 70 years after that atrocity, his son has visited Scarning Primary School to ensure his father's story lives on in the community for decades to come.
William O'Callaghan moved to the village, near Dereham, in 1930, and served as a volunteer in the Territorial Army before enlisting in the 2nd Battalion of the Royal Norfolk Regiment, where he became friends with Albert Pooley.
Yesterday, Pte O'Callaghan's son Dennis told a group of 60 seven and eight-year-olds the story of Bill and Bert, and the parts played by Madame Creton, evil Fritz and Col Scotland.
Ptes O'Callaghan and Pooley were the only survivors when German soldiers machine-gunned and bayoneted 99 British soldiers who surrendered in the French hamlet of Le Paradis, near Dunkirk, in May 1940.
Mr O'Callaghan told his audience how his father, despite being shot in arm, carried the wounded Bert through mud and rain to a pig sty where they survived on dirty water and raw eggs and potatoes before receiving help from Madame Creton.
Bert was repatriated because of his injuries, but Bill spent five gruelling years as a prisoner of war, much of it in Poland.
After the war the two friends had to convince sceptical British authorities that the massacre had happened, but they eventually met Col Scotland of the War Crimes Investigation Unit and testified at the trial of German commander Fritz Knoechlein.
Dereham has already honoured Pte O'Callaghan, who died in 1975, with a statue in its Memorial Hall of him carrying Pte Pooley, and William O'Callaghan Place named after him.
Yesterday his son Dennis brought his story to life for the next generation with a presentation that combined photographs, books and objects.
Speaking afterwards, one pupil said: 'I think he was angry because his friends were dead. I think he must have been quite tired but I think he was quite brave and worn out.
'I think it was quite amazing. He was a really, really special person and he survived. It was really interesting. I want to go there on a school trip.'
A boy in the same class said he was most impressed by the fact Bill and Bert somehow survived, and added: 'I think he would have been very stressed because with a lack of sleep you can be stressed, and then all the soldiers were dead.'
Mr O'Callaghan said: 'I think the reaction has been absolutely fantastic. During the presentation they were all interested in what we were talking about and another generation learns about Bill O'Callaghan.
'I think it's because he was a local man. He was a Scarning person and he was local and it's local history.
'We should not be allowed to forget the sacrifice of what our fathers did to make sure our country can go forward as it can now, in freedom.'
John Head, who with Mr O'Callaghan has spent 10 years ensuring the story lives on, said: 'I'm just absolutely stunned by how receptive the children were. I think it's incredible.
'They are showing empathy and they are in the shoes of Bill and Bert.'
And as if to prove his point, as the two men prepared to bring the session to an end, the boys in the class were discussing who would play Bill and who would play Bert in their playground re-enactments.
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