Langer leads by example
Centuries from Justin Langer and Ian Blackwell led a Somerset revival with an unbroken stand of 200 after they had earlier bowled out Surrey for 326 on day two at Whitgift School.
Langer (111), although dropped on nought by Mark Butcher, went on to score his 83rd first-class century from 141 balls with twelve fours and a six.
Blackwell (104) was also dropped at slip, when on 76, completing his century from 111 balls with eight fours and three huge sixes as Somerset closed on 335 for four, giving them a first-innings lead of nine.
Earlier Jonathan Batty completed his second successive fifty finishing with an undefeated 58 after almost four hours at the crease, facing 186 balls with eight fours as Surrey picked up just three batting points.
Resuming the day on 280 for seven overnight, Batty and Saqlain Mushtaq added a further 37 runs before Saqlain fell to the bowling of Charl Willoughby for 14. In trying to force through the leg-side, the Surrey spinner was beaten by the movement off the pitch and trapped lbw.
Surrey lost their ninth wicket in the next over when Dernbach was bowled for a duck by Alfonso Thomas, beaten by the late swing as he played down the wrong line.
The innings was wrapped up four overs later when Pedro Collins fell in the same way, looking to drive a ball that swung away, and saw his stumps knocked out of the ground.
Somerset got off to a flying start with openers Marcus Trescothick and Neil Edwards quickly sharing a stand of 67 in 17 overs before Dernbach deceived Edwards (40) with some late swing as the left-hander look to clip off his legs.
Just five runs were added before Dernbach picked up the important wicket of Trescothick for 30. The former England opener pushed forward, found the edge and Butcher took the catch at slip.
It was a chance that Surrey regretted as Langer and Blackwell steadied the ship.
However, they lost James Hildreth soon after without scoring, trapped leg before playing across the line to a full toss from Collins.
Zander De Bruyn smashed a quickfire 41 from 45 balls but then edged a turning ball from Saqlain in the 32nd over to Matt Nicholson at slip who grabbed the ball at the second attempt.