Born Nicholas Wertheimer (or Wertheim) in London in 1909, Winton was the son of German Jewish parents who had arrived in England two years earlier. In an effort to assimilate, his parents would later change the family name to Winton and have Nicholas baptized in the Anglican church. After leaving school without his degree, the multi-lingual Winton worked a series of finance jobs throughout Europe before returning to England to work on the London Stock Exchange. He became increasingly involved in left-wing politics, including vocally opposing what many considered the appeasement policies of the British government towards Nazi Germany—which culminated with the signing of the Munich agreement in September 1938, permitting Nazi Germany’s annexation of the “Sudetenland” portion of Czechoslovakia.

Three months later, his friend Martin Blake asked the then 29-year-old Winton to cut short a planned European vacation to join him in Czechoslovakia, where Blake had begun work on behalf of Czech refugees. Winton was shocked by the conditions he found. While work was being done to try to save Jews in Germany and Austria, comparatively little was being done to aid the most vulnerable, including children, in Czechoslovakia.

Although Jewish immigration to most western countries had been severely curtailed, Britain was a rare exception. In late 1938 (shortly after the Kristallnacht attacks in Germany) it established the Kindertransport program, which allowed for the entry of children under the age of 17 provided the refugees had host families in the United Kingdom. A £50 bond was paid for their eventual return to their homeland.

Winton quickly got to work, meeting with parents and gathering information on as many as 5,000 children in immediate danger. When his work aroused suspicion with Nazi officials, Winton used his own money for bribes. When the paperwork permitting the planned train transports to cross borders became snarled in bureaucracy, more handouts (and, eventually, forged documents) were dispersed. And when his Prague hotel room became insufficient for the increasing workload, he opened a small office, staffed by a few volunteers, which eventually registered more than 900 children for the Kindertransports.

Armed with photos of the Czech children, Winton returned to Britain, where he and a group of friends and family, including his mother, began recruiting host families. Although the refugees were primarily Jewish, they were placed with Jewish and non-Jewish families alike, a point of contention between Winton and some of England’s Jewish leaders.

By March 14, 1939, the first transport—the only one to travel by air—was ready to depart. Just one day later, the Nazis swept through much of the rest of Czechoslovakia. Seven more transports would follow in the next five months, carrying a total of 669 children to safety across the English Channel.

Despite this remarkable success, Winton would remain haunted by the ninth planned transport. Slated to depart on September 3, 1939, it was to have carried 250 children—the largest group yet—to safety. However, the German invasion of Poland on September 1 brought the Kindertransports to an immediate halt, closing all borders. None of the 250 children registered for the last transport were ever heard from again.

Following the outbreak of the war, Winton—a conscientious objector—worked for the Red Cross and later served in the Royal Air Force (RAF). He continued his humanitarian efforts after the war, initially joining the newly formed International Refugee Organization and then working with the International Bank for Reconstruction and Development. It was while working for the IBRD that Winton met his future wife, the Danish-born Grete Gjelstrup. The couple settled in Maidenhead, England, where they raised three children. Winton found work in the financial sector, unsuccessfully ran for local office—and kept largely silent about his role in the Czech Kindertransports.

It was a silence that would hold until 1988, when Grete came across a scrapbook in their attic that detailed Winton’s work, including intact lists of the 669 children and the addresses of their British host families. Grete passed the scrapbook on to Elizabeth Maxwell, a Holocaust scholar and the wife of a prominent newspaper magnate.

Widespread attention and accolades soon followed, with many comparing Winton’s work with that of German industrialist Oskar Schindler (who helped save the lives of 1,200 Jews) and Swedish diplomat Raoul Wallenberg, whose heroic efforts to save Hungary’s Jews ended with his death in a Soviet prison camp in 1947. Winton did not embrace the comparison, minimizing his own role in the Kindertransports (he had spent less than a month on the ground in Prague), and deflecting attention to his trusted lieutenants, who had faced a more immediate threat at the hands of the Gestapo.

Despite his feelings, Winton was knighted by Queen Elizabeth II in 2003, and additional honors would follow; Czech astronomers named a newly discovered minor planet after him and in 2014 he was awarded the Order of the White Lion, the nation’s highest honor, by Czech President Milos Zeman.

Perhaps the most moving tribute took place on September 1, 2009, the 70th anniversary of the ill-fated final Kindertransport. A specially-designed “Winton train” departed Prague’s main railway station for London. Onboard were some of the children saved by Winton’s remarkable humanitarian effort. When they arrived in London three days later, the 100-year-old Winton greeted them, just as he had in 1939. Today, there are more than 5,000 direct descendants of the children of the group affectionately known as “Winton’s children.”