Scott Newman and Mark Ramprakash shared a second-wicket stand of 187, with Ramprakash unbeaten on 174 at stumps his seventh century in his last 11 County Championship matches as Surrey finished day two of their Second Division match on 417 for 2, a lead of 70 over Northamptonshire's first-innings score of 347.
Their stand was only broken when Newman, on 143, was out to a breathtaking catch by Ben Phillips.
Alex Tudor turned in his best performance for four years to give Essex a firm grip on their Second Division match against Somerset at Southend. The 28-year-old fast bowler took 5 for 67 in 19 overs as the visitors were all out for 133, a first-innings deficit of 119. By the close, Essex had stretched their advantage by a further 208 for the loss of four wickets.
It was the first time since August 2002, when Tudor was with Surrey, that the former England fast bowler had taken five wickets in an innings. Darren Gough gave him fine support, finishing with 4 for 41.
Andy Flower maintained Essex's dominance with the bat, hitting60 from 64 balls. Essex's captain, Ronnie Irani, was unbeaten with 30.
* The England and Wales Cricket Board is set to employ the three appeals rule rejected by the International Cricket Council in July in next summer's Cheltenham & Gloucester Trophy. Players can appeal against umpires' decisions, but only in televised games.