Nicholas Winton, a 29-year-old stockbroker from London, was planning a skiing holiday in Switzerland. He never got there. Instead he received a telephone call from a friend in Prague: "Come to Prague. We need you." In Prague, he found a refugee crisis.
It was 1938, and Hitler had invaded Czechoslovakia. Many were trying to get out of the country, or at least get their children out. Winton set up an office in his Prague hotel. He was in Prague for only two or three weeks, but on his return to London he worked for eight months in his spare time, raising money, finding foster homes and obtaining travel documents.
In nine months he arranged eight trains to bring 669 children, mainly Jewish, to safety in England. Many of their families perished in Auschwitz The trains stopped when Hitler invaded Poland and the borders were closed.
For 50 years Winton didn't speak of what he had done, even to his wife. (He had married in 1948.) Then in the 1980s his wife found children's photographs, a list of children's names and addresses and letters from parents in their attic. Word spread. Winton was invited to a television programme as part of the studio audience, and found the programme was about him.
Nicholas Winton died on Wednesday, aged 106.
You can see here a video about his life. It includes a moving moment from the television programme, where the presenter asked if there was anyone present who owed his or her life to Nicholas Winton. It looked like almost the entire room stood to their feet.
He was given a knighthood for his service to humanity, and the Order of the White Lion, the Czechs' highest honour. It is estimated that almost 6,000 people - the children and their descendants - are alive because of Sir Nicholas Winton.
"I work on the motto that if something's not impossible, there must be a way of doing it," he said.