Nothing has quite the same screen allure as a secret world. Espionage is so secret, by definition, that we have to take even its existence as a matter of trust; all we know about what goes on behind the intelligence agencies’ closed doors is what is relayed to us through books, films and series like A Spy Among Friends, based on Ben Macintyre’s book about the British double agent Kim Philby. Presumably, a certain kind of person is drawn to that world where nothing can be let slip outside it. To work for both sides, one must constantly be aware of who said what to whom, who knows what, who saw you where, who remembers you there — that anyone should want that life is a mystery in itself.