Embrace all, trust none. (Don’t trust gadgets either.)
Sidney Reilly (born Rosenblum) is reputed to be the greatest spy of all time, celebrated as the Ace of Spies.
It was Reilly who coined this motto: Trust no one.
(Reilly eventually got himself killed—by the Bolsheviks in Russia—for trusting someone running something called—of all things—The Trust.)
As a spymaster, embrace everyone, especially your enemies. In The Art of War, Sun Tzu writes: Keep your friends close and your enemies closer.
The Monaco spymaster’s mentor was Clair George, who rose through the ranks of the Central Intelligence Agency to become America’s spymaster as Deputy Director for Operations.
Clair George embraced everyone. If they represented the enemy, he plucked secrets from their back pocket while exchanging hugs.
Clair George would convince the enemy to like him, and to trust him. And the next step would be to convince the enemy to pass him vital secrets.
Clair George was not as trusting as those he cultivated and recruited.
Adversarial intelligence services would, of course, try to cultivate and recruit him. And Clair would embrace them. But he did not trust them with the knowledge of anything that could be used against himself or his country.
Trust no one.
The only real secret is one that you know and you don’t tell anyone else.
Clair George also never trusted gadgets, such as listening devises. They could go wrong; they would go wrong.
Clair relied on a good memory and good note taking—perhaps two of the most important attributes of an intelligence officer.
None of this was lost on Monaco’s spymaster.
And by the way: the greatest spy of all time was Clair George, not Reilly.