Columbia subject headings:
Harvard subject headings:
Great Britain. MI5--History.
Spies--Germany.
World War, 1939-1945--Prisoners and prisons, British.
World War, 1939-1945--Prisoners and prisons.
World War, 1939-1945--Secret service--Germany.
Princeton subject headings:
Great Britain. MI5--History.
Intelligence service--Great Britain--History--20th century.
Spies--Germany.
World War, 1939-1945--Military intelligence--Great Britain.
World War, 1939-1945--Prisoners and prisons, British.
World War, 1939-1945--Secret service--Germany.