The roll call of Britain’s greatest spymasters includes Vernon Kell of MI5, Mansfield Cumming (the original “C”) of MI6, and Colin Gubbins of SOE. Yet Thomas Kendrick, the subject of this book, may have been the most influential of them all. Why, then, haven’t we heard of him? He “left no unpublished memoirs or interviews about his life”, notes Helen Fry, and there were no obituaries to him after his death. Undeterred, Fry has painstakingly pieced together Kendrick’s extraordinary life and wartime achievements by interviewing his grandchildren and working through hundreds of declassified files. The end result is a remarkable piece of historical detective work.

Born in Cape Town in 1881, the son of an American merchant and his South African wife, Kendrick was educated by Jesuit priests at the prestigious St Aidan’s College, Grahamstown, a background that enabled him “to slip later into the ‘public school network’ of the British secret service”. His first experience of intelligence work was serving with the Cape Colony Cyclists Corp, a unit that carried out reconnaissance behind enemy lines during the Anglo-Boer War of 1899-1902. During the First World War, he conducted field intelligence and counter-espionage for the nascent MI6 – then known as MI1(c) – in France, the start of three decades “at the heart of European operations for British intelligence”.

Level-headed, with supreme analytical skills and personal charm, Kendrick “could navigate the egos of heads of departments and bring them together”. By 1925, he was passport control officer at the British Embassy in Vienna, a cover for his actual role as MI6 head of station, running spy networks across Europe and gathering vital information on the threat from Soviet Russia and, later, Nazi Germany. By the autumn of 1927, for example, he had compiled a complete list of Bolshevik sympathisers and activists for MI5 to track if they entered Britain.

In the early 1930s, Kendrick may have been briefly assisted by a brilliant young Cambridge graduate called Kim Philby. They moved in the same Vienna social circles and Philby, who later spied for the Soviets, was probably able to join MI6 in 1940 because he had worked with Kendrick. Another notable name on the spymaster’s payroll, risking her life to reveal Nazi secrets, was Countess Marianne Szapáry, the mother of Princess Michael of Kent.

Kendrick, however, was not infallible. In 1937, one of his deputies recruited Austrian inventor Karl Tucek to spy on the Nazis. Unfortunately, Tucek was already working for the Abwehr, Hitler’s military intelligence service, and his double dealings helped to dismantle Kendrick’s anti-Nazi spy network and force the spymaster to flee Austria after the country was annexed by Germany in early 1938.