More than two dozen of the children saved during the Holocaust by a man known as “Britain’s Schindler” will gather to remember him as a special service is held in his honour.

Sir Nicholas Winton, who died last year aged 106, founded the Kindertransport operation which brought 669 mostly Jewish children on eight trains from Nazi-occupied Czechoslovakia to London in 1939.

His death prompted tributes from Prime Minister David Cameron, who said the world had lost “a great man”, and then Ambassador of the Czech Republic to the United Kingdom Michael Zantovsky, who described him as “a positive man who radiated good”.

Sir Nicholas kept his bravery a secret for half a century – not even telling his wife Grete who only uncovered his selfless humanitarian efforts when she found an old briefcase in the attic containing lists of children and letters from their parents.

In 1988 his family took the scrapbook to Dame Esther Rantzen’s That’s Life to make a programme about what he had done.

The moment he was informed the lady sat next to him in the audience was Vera Gissing, one of the women his Kindertransport had brought to safety, was captured on camera and saw him wipe tears from his eyes as they hugged.

Among his many honours were an MBE in 1983 for his services to learning disability charity Mencap, a knighthood in 2003 “for services to humanity”, and the awarding of a Hero of the Holocaust medal at 10 Downing Street in 2010.

Others expected to attend the service at London’s Guildhall this afternoon are Dame Esther, representatives from the Czech and Slovak authorities and the British Government, and former Labour MP Lord Dubs who was another of the children saved by Sir Nicholas’s actions.

Considering the families many of the children went on to have, Sir Nicholas’s relatives estimate somewhere in the region of 7,000 people were able to live because of what he did.

A memorial concert, in aid of today’s child refugees and featuring actor Rupert Graves and cellist Alexander Baillie, will be held at St John’s Smith Square on Thursday.