Robert Pattinson was left "angry and upset" after discovering texts from Rupert Saunders on Kristen Stewart's phone the morning of his birthday.
The 'Water For Elephants' actor was looking at his on/off girlfriend's phone when he saw the messages from the director - who Kristen had an affair with when the pair shot 'Snow White and the Huntsman' - leaving him heartbroken on his 27th birthday on May 13.
He decided to leave right away, end their four-year relationship and told his 'Twilight' co-star to leave him alone.
A source told The Sun newspaper: "Rob was looking at her phone on the morning of his birthday as he wanted to take a picture of something when she was in the shower.
"Suddenly this message flashes up and it's not what he wanted to see. He got straight up and left. Despite Kristen's pleas, he told her not to come to his birthday party at his friend's that night.
"He's extremely angry and upset. No matter how many times she calls or texts, friends say he's had enough."
Despite the couple managing to patch things up after a two-month break following Kristen's "momentary indiscretion" with Rupert last year, it is thought their relationship is over for good this time after Rob was spotted moving his belongings out of her home in Los Feliz on Sunday, where they both lived over the last few months.
The source added: "After everything that happened and the hurt she caused, he's furious she'd be back in touch with him, even if she is saying it's completely innocent.
"It does look like this it's over for good. He simply can't trust her."