SIR PAUL MCCARTNEY is fuming after two American tourists broke into his English country estate and filmed themselves strolling around his private grounds. The trespassers broke into the former BEATLE's home in Peasmarsh, East Sussex - shooting their break-in with a video camera before posting the footage on popular filesharing website YouTube. A source close to MCCartney - who is currently undergoing divorce proceedings with estranged wife HEATHER MILLS - says, "MACca (MCCartney) is livid. He is supposed to have tight security to protect him and his family, but this pair walked straight in. It's lucky they were harmless. "He just didn't need something like this happening. The divorce is giving him enough stress." On the footage, a woman is heard commenting, "This is it. This is his house. It's a beautiful house. It's beautiful. Oh God, we're going to be in so much trouble." It is unclear whether MCCartney was in the house at the time. A spokesman for the rocker declined to comment.