The Libertines star struck up an unlikely friendship with the model/singer after relocating to Paris, and he was even invited to take part in music sessions with her at France's official residence, the Elysee Palace.
Doherty has now revealed he "connected" with Bruni when they opened up about their fears of performing on stage.
He tells Britain's The Guardian newspaper, "She was surprised to hear I actually have a lot of trouble going on stage. Nervous isn't the word, I get twisted. And she says it's the worst place in the world for her to be, she hates going on stage, especially in France because she feels that people hate her, she says they're out to get her, basically."
He reveals spending time at the house she shared with Nicolas Sarkozy, then president of France, was "really strange" because "you've got a guy with a submachine gun on each door".
However, the rocker gained a rare insight into the couple's relationship: "All the time, I was aware that she's just devoted to this guy. She said that in another world, if he'd been a farmer and she'd been a bakery girl, they still would have been together."