David Oppenheim Doubles Up

With the board reading [Ad3c3hKs], the player in the big blind checks, and David Oppenheim bets 2,500 into a the pot of 5,000 or so.  The river brings the [Jh] and the big blind checks again.  Oppenheim moves all-in for 4,525 and the other player thinks a minute before calling with [AcQc].  Oppenheim shows [AhJs] for aces and jacks and doubles up to 20,000.