Former editor of The Times James Harding joined his cousin Thomas at Belsize Square Synagogue on Sunday in a book launch chronicling the untold story of the pair’s great-uncle, Hanns Alexander.

Part history, part biography and part true crime, Hans and Rudolf reveals the astonishing story of the pursuit and capture of one of Nazi Germany’s most notorious war criminals, Rudolph Hoss.

Penned by Thomas Harding, the pair spoke of their great-uncle’s journey from being the son of a prosperous German family to a refugee in London during the 1930s.

After serving in the British Army during the Second World War, Alexander, who settled in Belsize Park after fleeing Berlin, was chosen as a member of a 12-man team tasked with hunting down Nazi war criminals.

The book goes on to chronicle the search for Hoss, an SS commandant of Auschwitz concentration camp, where more than a million Jews were murdered.

After a year of escaping arrest, Alexander’s hunt for Hoss finally ended when he was captured in 1946.

He was hanged the following year.

The book launch was held at the synagogue in Belsize Square.