The generally icy-cool R-Patz recently lost his temper when girlfriend Kristen went out with co-star Garrett Hedlund. The Twilight actor does not seem to like the fact that while he is away in London, his girlfriend hangs out with 'friend' Garrett.

“Rob went home to London to spend Christmas with his family and Kristen stayed in the States to spend Christmas with her family. They both agreed on spending the holiday apart, but would ring in the New Year together,” an insider told Hollyscoop. “But, on Christmas Eve, Kristen hit the town with Garrett and when Rob heard about he got really jealous. She knows that Rob is jealous of Garrett and to go out with him while he’s miles and miles away did not sit well with him”.

“They had a huge fight over it”, the source continued. “Kristen didn’t mean anything by it. Garrett is her friend and he happened to be around. She was apologetic to Rob, but that didn’t satisfy his jealousy. After they hung up, Rob called on some friends and went out hitting the pubs in London. Kristen tried to call Rob on his cell, but he wouldn’t pick up. He finally called her the next day and they two smoothed the whole thing out. They will be spending New Year’s Eve together”.

Glad to know that it was nothing more than a lovers' spat and also that beneath that cold emotionless exterior, lies a hot-blooded young guy like the rest of us!