Vikram Solanki made his first Surrey century as his side threatened Sussex's unbeaten record in the LV= County Championship after dominating the third day at Arundel.
Solanki, leading the county because of injuries to Graeme Smith and Gareth Batty, struck the 22nd first-class hundred of his career with a stylish 130 while Zander de Bruyn made an unbeaten 99 as Surrey reached 362 for six at stumps, a lead of 67.
The first day's washout means the draw still looks the likeliest outcome but Sussex, who lost top spot in Division One earlier in the day following Yorkshire's victory over Middlesex, are facing a rearguard action with the bat for the third game running.
Until Solanki and de Bruyn came together shortly after lunch, the game was evenly poised. Surrey openers Arun Harinath and Rory Burns put on 56 before Chris Jordan found some extra bounce in his second over to have Harinath well taken low down at third slip by Ed Joyce.
It was Jordan's 35th wicket since his winter move from Surrey and he showed his prowess at slip either side of lunch with two superb catches as Burns was held one-handed trying to run the ball down to third man before Ricky Ponting was squared up by Steve Magoffin to give Jordan a more straightforward catch.
That left Surrey 113 for three but they strengthened their position during the afternoon in a fourth-wicket stand of 177 in 41 overs between Solanki and de Bruyn.
For the first time in the game, a batsman had the measure of the slow pitch as Solanki, particularly strong through the off side, hit 11 fours and two sixes, the first of which landed next to a startled dog in the press tent.
He added four more boundaries in smooth acceleration to 130 before holing out to long-on having faced 179 balls.
Surrey looked to kick on thereafter but their progress was stalled by the loss of two further wickets. Steven Davies, promoted up the order, was caught behind to give Monty Panesar his third wicket.
And, although 16 runs were conceded by Magoffin in the first over with the second new ball, including five penalty runs when a stray throw hit a helmet, Sussex struck again when Jordan squared up Gary Wilson, who edged to Michael Yardy at second slip.
De Bruyn has had a modest summer so far with only one half-century in 11 previous championship innings and while he struggled to match Solanki's fluency he was still there at the close, having faced 176 balls and hit 10 fours and a six.