Happy slap killer ‘beat up girlfriend twice’

A convicted ‘happy slap’ killer who filmed the horrific attack on her phone assaulted her girlfriend with so much force she fell through a barrier into a building site, a court heard. Chelsea O’Mahoney, 30, was 14 when she recorded her friends kicking a gay barman to death during an all-night rampage of violence around London’s South Bank in 2004. She told 27-year-old David Morley: ‘Pose for the camera’ as he was savagely battered by the Clockwork Orange-style gang before…