Chris Nash struck his first hundred of the season as Sussex comfortably negotiated 59 overs on the final day at Arundel to draw with Surrey and maintain the only unbeaten record in LV= County Championship Division One.
The visitors earlier declared on 456 for nine with a lead of 161, leaving Sussex to bat through much of the final day for the third successive game to stave off defeat.
An opening-wicket stand of 107 between Luke Wells and Nash calmed any nerves, the latter going on to a chanceless century - the 14th of his first-class career - just before stumps.
Nash had only passed 50 once previously this season, when scoring 80 in the opening game against Yorkshire.
Yet he had few alarms on a placid, slow surface and hit 11 fours in his unbeaten 102, which came off 177 balls. Sussex declared their second innings on 201 for two, a lead of 40, when the players shook hands at 4:50pm.
Earlier, Chris Tremlett hit his first half-century for three years as Surrey collected maximum bonus points for the first time this season.
Surrey needed 12 off the 110th over to secure a fifth batting point and Tremlett got the runs in two blows, lofting Steve Magoffin over deep midwicket for six before pulling his next ball square.
He hit two more sixes and three boundaries as he reached a 29-ball fifty with Tim Linley, who struck Monty Panesar for a maximum, giving him good support in a ninth-wicket stand of 74 from just seven overs.
Tremlett eventually holed out for 54 while Panesar picked up the other two wickets to fall on his way to a first five-wicket haul of the season.
The England left-arm spinner had Zander de Bruyn taken at cover for 111, the South African having collected the single he needed to go to his first hundred of the season in the third over of the day. De Bruyn faced 202 balls, hitting 11 fours and a six.
Sussex lost two wickets to left-arm spinner Zafar Ansari when they batted again. Wells took his aggregate against Surrey to 528 runs from his last six innings with a 91-ball half-century, which included six fours, but was caught at slip by Gary Wilson soon after.
Michael Yardy gave Ansari his second success when he pushed forward and was held at short-leg with the score on 131 but, by then, Sussex were all but safe.