Check Raise for Impressive Andersen

Stephen Andersen is having rather a good day today. Each time we walk past his table he is involved in a pot. Here he is clashing with the Englishman Keith Johnson.  

Stephen Andersen opens to 1,900 and Keith Johnson makes the call. The pair stare at a flop of [Ac] [7s] [2s], Andersen checks, Johnson bets 2,000, Andersen check-raises to 8,000 and Johnson folds.