LONDON - Concert organizers pulled the plug on rock stars Bruce Springsteen and Paul McCartney after the pair defied the sound curfew at London's Hyde Park. McCartney joined Springsteen at the end of the singer's headline gig Saturday night, but both stars had their microphones silenced before they could address the crowds. Springsteen had already exceeded the 10:30 p.m. curfew by half an hour when he welcomed McCartney on stage and the pair sang the Beatles hits "I Saw Her Standing There" and "Twist and Shout." But neither performer had the chance to thank the crowd, leaving the stage in silence. Steven Van Zandt, who plays guitar in Springsteen's E-Street Band, criticized the decision as heavy-handed. "On a Saturday night! Who were we disturbing?" he said on Twitter.