Summers published "The File on the Tsar" with former BBC colleague, Tom Mangold, in 1976. The book is on the disappearance and presumed execution of Nicholas II, last Tsar of Russia, and his family. In the UK, "The Sunday Times" said it "demolished the massacre story beyond recovery. There is not a dull page in this book." In the U.S.A., the "Los Angeles Times" called it "a compelling and impressive work", "Cosmopolitan" deemed it "sensational...a masterful work of great suspense, meticulously researched". In a comparison that must surely have pleased the authors, "The Toronto Sun" rated the book's "superlative investigative reporting that makes Woodward and Bernstein seem like beginners."