British author of espionage novels David John Moore Cornwell, better known by his pen name John le Carré, died Saturday of pneumonia at Royal Cornwall Hospital, at the age of 89, according to his agent.

Jonny Geller, CEO of The Curtis Brown Group and le Carré’s agent, said, “John le Carré was an undisputed giant of English literature. He defined the Cold War era and fearlessly spoke truth to power in the decades that followed. I have lost a mentor, an inspiration, and most important, a friend. We will not see his like again.”

Before penning the spy novels, Le Carré worked as a British intelligence officer himself. He wrote his first three books while working for Britain’s MI5 and MI6. He then became a full-time author with the publication of his third novel, “The Spy Who Came In From The Cold,” in 1963.

One of the formative figures in le Carré’s life was his father, Ronald Thomas Archibald (Ronnie) Cornwell, a flamboyant con man and criminal who was in and out of jail, leaving his son to be raised in boarding schools.

Once le Carré told Terry Gross, “He [his father] filled my head with a great lot of truthless material, which I found it necessary to check out as a child, with time. Yes, in that sense, these were the early makings of a spy.”

He wrote 25 novels and one memoir. He sold over 60 million copies of his work worldwide. He published his last novel, Agent Running in the Field, in October 2019.

Born on October 19, 1931, in Poole, Dorset, England, le Carré won the Olof Palme Prize in early 2020 for what organizers called his “engaging and humanistic opinion-making in literary form regarding the freedom of the individual and the fundamental issues of mankind.”

He donated the $100,000 prize to Médecins Sans Frontières, aka Doctors Without Borders, an international humanitarian medical non-governmental organization. Le Carré is survived by his wife, four sons, 14 grandchildren, and three great-grandchildren, according to NPR.