Simple phrase used to catch out
British spies or agents when masquerading as the enemy. When wished '
Good luck' in English by a foreign agent they find it literally impossible not to reply with 'Thanks old
bean!' or something similar.
Most famously used in The Great Escape.
Hans Nazihausen: Halt! Sprechen sie Englisch?
John Smithson: Nein! Der English sind Schwein-poopen.
Hans: Haha, Ja. Good luck.
John: Thanks old
bean!
Hans: AHA!
John: Oh bother.