I've just looked again at all angles and pause-motion and both hands are on the no. 8's shoulders. Caulker's left hand is actually over the defender's left shoulder and he grabs the front of his shirt and pulls his shoulder back. Unfortunately the ref had a good view of it. We really must practise these set-pieces and if Caulker is going to do this sort of thing then we need somebody to block the referee's line of sight.