A 110-year-old lemon used by a German WW1 spy to send secret messages from Britain with invisible ink is going on display in ...

Spy used pen nibs dipped in lemon to write invisible messages to his counterparts. He relayed his secrets in between lines of ...

A passport belonging to one of the Cambridge spies, a 110-year-old lemon used for invisible ink and a letter about ... London's Reform Club by Cambridge spy Guy Burgess as he fled to Moscow ...