Kind-hearted Rudi Schoberl, 96, risked certain execution when he took pity on widowed Netta Hallett and her eight children.
Then a 23 year-old, he was posted on the Channel Island in 1943 when he sent messages to Hitler's pilots encoded by the famous Enigma machine.
Despite being banned from fraternising with locals, he exchanged his cigarette rations for precious food for them - even though having barely enough to eat himself.
Grateful Netta and her children struck up an unlikely friendship with Rudi and they never forgot him after the end of the war - which he finished in a PoW camp.
Netta returned the kindness by sending him food parcels, including Guernsey butter which he had come to love.
Rudi proudly told his PoW captors the food had come from his 'Guernsey mum'.
He was finally released in 1948 and set up home in Essex and falling in love with the English way of life.
He remained in contact with Netta and her family and went back to Guernsey to visit them a couple of times, the last in 1974.
But for the first time in 43 years he has gone back to Guernsey, accompanied by daughter Carol Mallis, granddaughter Kelly Israel and great-granddaughters Xanthe, six, and Ariadne, three.
They have spent several days with Netta's daughter Loretta Winterson who was a 13 year-old girl when he helped her family.
Lorretta, 86, said: "He did so much to help my mum - our dad died just before the war started and the baby wasn’t born yet.
“He was so good to us and he’s wonderful even now, at his age.
“He risked his life with so many of the things he did for us.
"If he’d been caught, they would have shot him. Those little things, they didn’t tolerate.”
Her sisters Joyce, 83, Margaret, 80, and Sheila, 77, and brother Brian, 78, joined them at the reunion.
Loretta added: “Rudi has been here for three days and he has not stopped talking about the war.”
Rudi told them of the hardships he suffered as a young wartime recruit when he ate cats, dogs and rats which were skinned and spit-roasted over an open fire.
He also told them how he helped another family in occupied France before being posted to Guernsey.
Rudi said: “I think back and I wonder how I got away with it. My whole life was just helping people, I have no regrets.”
And he said his mother showed the same kindness in their native Germany, taking food to Russians in a prison camp near the family home.
She was caught twice, and the second time warned by the German authorities that a third time would see her taken to a concentration camp.
But she was undeterred and carried on her secret acts of kindness and managed to avoid detection.
After the war she encouraged Rudi to stay in England.
Loretta said: “His mum said ‘are you happy in England?’ and Rudi said ‘yes.’
“She said ‘I think you should stay there then.”
Rudi married an Englishwoman, Joyce, and set up home in Essex - but found that few people would speak to him because of his wartime past.
He laughed at the memory of one report in a local newspaper.
“It said ‘If you want a council house, join the German air force,’” Rudi said.
He has spent his life since in England and celebrated his 96th birthday in June by taking to the skies again in a plane.
Loretta said: “Rudi is now in an old folks home but he still gets around and eats like a horse.”