Surrey 262 and 44 for 3 lead Essex 180 (Walter 64, Clark 3-33, Worrall 3-40) by 126 runs
Fourteen wickets fell on an attritional day two at the Kia Oval as Surrey edged themselves ahead against Essex in a top-of-the-table contest that could have a significant bearing on the destination of this year's Vitality County Championship title.
Division One leaders Surrey, resuming on 248 for eight, at least made sure of a batting bonus point before being bowled out for 262 but second-placed Essex, missing an ill Jordan Cox, were then dismissed for 180 in their own first innings.
And, on a well-grassed pitch giving assistance to the quicker bowlers, Surrey then struggled to 44 for three in their second innings but still took their overall lead to an already handy 126.
Only Paul Walter, who top-scored with 64, and Matt Critchley, with a determined 48, held up the Surrey seam attack for any length of time - but Jamie Porter, Shane Snater and Eathan Bosch all struck new-ball blows for Essex before bad light lopped 27 overs from the day's allocation.
Cox's absence was particularly unfortunate for Essex, with the in-form 23-year-old - who has scored 763 championship runs at an average of 69.36 this season - reportedly needing to have an appendix operation after leaving the field yesterday feeling unwell.
Dan Worrall and Jordan Clark took 3 for 40 and 3 for 33 respectively for Surrey, with Worrall chiefly responsible for Essex's initial slide to 113 for five. Clark followed up his crucial early strike to remove former South Africa Test captain Dean Elgar for a 19-ball duck by later ending Walter's combative 64 and finishing off the innings by having Bosch caught at mid on for 12.
Walter, who struck Clark for six and also hit eight fours - several of them booming off drives - was eventually eighth out when he miscued a hook to deep square leg.
Essex began badly with Nick Browne edging Worrall to third slip on 12 and fellow opener Elgar following in the next over when Jamie Smith held on again in the same position as the probing Clark found reward for his sustained accuracy with the new ball.
Tom Westley made 11 before losing his off stump to a magnificent ball from James Taylor but Critchley and Walter then added 52 either side of lunch, with Critchley hooking Tom Lawes for six to go to 32.
Worrall returned to remove Critchley with an outswinger prodded to second slip, and Worrall struck again when Michael Pepper (1) slashed straight to square cover.
Simon Harmer offered some lower order resistance, pulling Taylor for four and then on-driving him next ball for another boundary, but on 16 was pinned leg-before by the same bowler.
And Lawes, in his first appearance for two months due to a heel injury, looked more dangerous in his second spell and had Snater caught by Taylor at long leg for six.
Tea was taken immediately after Clark wrapped up the Essex innings but Surrey then lost both openers in quick succession as Dom Sibley was bowled off stump for 11 by an absolute beauty from Porter and Rory Burns edged Snater to second slip to go for eight.
Bad light first forced the players off at 5.09pm, with Surrey on 36 for two, and on a resumption at 5.37pm Dan Lawrence was adjudged lbw for 10 to Bosch, playing no stroke to one angled back into him.
But only two overs were possible in this mini-session before more bad light drove the players off again at 5.51pm, umpires Peter Hartley and Graham Lloyd then waiting patiently for more than an hour until the light improved enough for a final four overs to be bowled from 7.02pm.
At stumps at 7.17pm Smith had moved on to 11 not out, with Ben Foakes unbeaten on four and having already taken a blow on his right hand from a Porter lifter.
