A former bodyguard has rained on Brangelina’s double Oscar nod joy by announcing that he is penning a scandalous tell-all book about the Changeling actress.

Beefy bodyguard Mickey Brett, who served as Angelina’s head of security for seven years, was so close to the pouty-lipped star that her oldest son, Maddox, used to refer to him as “Uncle Mickey.” But after being abruptly fired by the famous couple after a long-running feud with Brad in 2007, Mickey, 52, decided to team up with ghostwriter Robin McGibbon and use the power of the pen to dish the dirt on the mother of six.

“It will include the sordid details of how they got together while Brad was still married to Jennifer Aniston,” a publishing industry informant has revealed to In Touch.

Mickey claims to have walked in on the Brad and Angelina having sex while filming the 2004 smash Mr. & Mrs. Smith.

“Mickey walked in on Brad being intimate with Angelina in her trailer.”

And if that wasn’t salacious enough for you, the upcoming tell-all promises tidbits about Brangelina’s sex life.

“She indulged any fantasy he had, including buying sex toys, paddles, whips, and dressing up in latex.”

The security guard alleges that Angie is a habitual cheater who began having a “secret rendezvous” with an infamous female pop star after the birth of the couple’s daughter, Shiloh.

“Mickey set up at least 20 meetings for Angie with this woman at hotels when Brad was working,” says the In Touch spy.

“This is Angelina’s worst nightmare. She trusted Mickey to keep her secrets….This may end their relationship. She’s terrified Brad may leave her when he hears about the mean-spirited things she said about him behind his back and her secret relationships.”