Columbia subject headings:
Harvard subject headings:
Espionage.
Intelligence service.
Princeton subject headings:
Authors, English--20th century--Biography.
Espionage, British--Fiction.
Espionage, British--History--20th century.
Fiction.
Great Britain. MI6--Fiction.
Great Britain. MI6--History--20th century.
Intelligence service--Great Britain--Fiction.
Intelligence service--Great Britain--History--20th century.
Spies--Great Britain--Biography.
Spies--Great Britain--Fiction.
Spies--Great Britain--History--20th century.
Spy stories, English.