Dec. 13 (UPI) -- British best-selling author David Cornwell, better known as John le Carre whose Cold War-era spy novels transformed the espionage genre, died over the weekend, his literary agent said. He was 89 years old.
His family said le Carre died Saturday night in Cornwall, Britain, from pneumonia after a short battle with the illness.
"I have lost a mentor, an inspiration and, most importantly, a friend," he said. "We will not see his like again."
Geller described le Carre as "an undisputed giant of English literature" who "defined the Cold War era and fearlessly spoke truth to power in the decades that followed."
Le Carre's literary career spanned nearly six decades and included 26 books, including The Spy Who Came in From the Cold, the 1963 novel that placed his name among the very best of the spy genre with his plump and balding spy, George Smiley, critiquing Ian Fleming's dapper and handsome James Bond.
His literary career began near the tail end of his time working for the British intelligence service.
In the late 1950s, he spied on far-left groups seeking information on possible Russian agents before transferring to the foreign intelligence service, known as MI6, in the early 1960s, according to publishing house Penguin Random House Canada.
"From the day my novel was published, I realized that now and for ever more I was to be branded as the spy turned writer, rather than as a writer who, like scores of his kind, had done a stint in the secret world, and written about it," he wrote in a postscript to the novel. "The novel's merit, then -- or its offense, depending on where you stood -- was not that it was authentic, but that it was credible."
Along with The Spy Who Came in From the Cold, several of his novels have been turned into films, including Tinker Tailor Soldier Spy in 2011, which received three Oscar award nominations.
Actor Gary Oldman, who starred in the film as Smiley, said le Carre was the "true owner" of the serious spy genre and all who follow are in his debt.
"His characters were drawn deftly and deeply, nuances too many to count, and for me, inhabiting George Smiley remains on of the high points of my life," Oldman said in a statement to Deadline.
He added he got to know le Carre during the shooting of the film and said he was always available to offer advice.
"He was generous with his creativity and always a true gentleman," he said. "The true spy master of several generations has left us."
Nicole Winstanley, the publisher of Penguin Canada and vice president of Penguin Random House Canada, said the death of le Carre was a loss for both publishers and readers alike.
"We have taken an extraordinary journey through the cultural political landscape with him, riveted by the stories he told," Winstanley wrote in a statement. "He will be greatly missed."
Le Carre is survived by his wife of nearly 50 years, Jane, and four sons.