Helena Bonham Carter's maternal grandfather, Eduardo Proper de Callejon, also rescued many Jews from the Holocaust, by forging Spanish exit visas.
The idea for the film came when producer Iain Canning saw a clip of Nicholas Winton on That's Life! (1973) and wondered about the story behind it. He and Emile Sherman, who, together, had recently established their See-Saw Films company, went to visit Winton, then 101 years old, in 2010. Canning describes him as "humble, generous and also incredibly kind," saying Winton was reluctant to be painted as a hero onscreen. "He believed that we all have the capacity to do the right thing at the right time," Canning recalls. A few years later, the producers enlisted screenwriters Lucinda Coxon and Nick Drake to adapt "If It's Not Impossible...: The Life of Sir Nicholas Winton," a 2014 biography of Winton written by his daughter Barbara Winton. She gave her blessing to the film - as long as her father was played by Anthony Hopkins.
In the newspaper obituaries after Sir Nicholas Winton died on July 1st, 2015, the UK press headlines dubbed him 'The British Schindler.'
The extras who stand in the That's Life! (1973) audience were played by those who owed their life the actual Nicholas Winton. Some were the actual children saved, recreating their roles in the audience from the original broadcast 35 years prior. The rest were the adult children and in some cases adult grandchildren of those that Winton had saved. Anthony Hopkins said in an interview that he did not know until filming that the extras were the real survivors and their descendants.