Dame Esther Rantzen has hailed Sir Nicholas Winton as “a hero” who “proved that one person can make such a difference” during a moving memorial service for the Holocaust hero.

Around 400 people attended the service this afternoon, including 28 of the 669 mostly Jewish children who Sir Nicholas helped escape from Czechoslovakia to Britain.

Theresa May, the Home Secretary, and both of Sir Nicholas’ children were at the public memorial. He died in July last year at the age of 106.

Speaking at the Guildhall in central London during the televised event, host Dame Esther - whose That's Life programme publicised Sir Nicholas’s story - told the audience that the man dubbed the “British Schindler” had “proved that one person can make such a difference.”

It is estimated that around 7,000 people owe their lives to Sir Nicholas, who Dame Rantzen said “continues to inspire generations of others to have his courage, and his capacity to inspire trust”.

Ruth Halova, who was in the crowd for the 1988 That’s Life episode, told the crowd she remembered having “no time to be frightened” on the Kindertransport train.

When asked by Dame Esther what her abiding memory of Sir Nicholas was, she recalled meeting him in 1989, 50 years after he saved her from the imminent Nazi invasion.

“I saw him at a hotel in Jerusalem, and he opened his arms wide. My father died when I was 10 months old, but Nicky was my father. He was always my father.

“I loved him dearly, and I think he was the biggest exemplar of humanity you will ever find.”

Fellow Kinder Hugo Marom told Dame Esther he represented the 18 people who were able to enjoy long, full lives because of Sir Nicholas.

“We invited Nicky to our house,” he said, “and for the first time all 18 of us realised the enormous effect he had had, not just on the Czech children but by bringing our story to the attention of the world.

“At a time when no-one was willing to accept refugees, Britain did.”

He asked the audience: “How is it possible that Nicholas Winton, in three weeks in Israel, inspired so many parents with just his glasses and Oxford accent?

“The great impression he made on them spread like fire.”

Karen Pollock, Holocaust Educational Trust chief executive, said: "Sir Nicholas Winton was a true hero of our time and an example to us all of the importance of standing up against injustice.

“We owe it to him to ensure that his brave actions and what they represent are never forgotten.

“This memorial is an opportunity to come together to celebrate his life and thank him for all that he did and we are proud to be a part of it."