Match scores (Chelmsford)
Essex beat Sussex by 10 runs
Essex inns: 295-7 (50/50 overs. Cook 109, ten Doeschate 102; Taylor 3-65)
Sussex inns: 285 all out (48.1/50 overs. Nash 66, van Zyl 61; Harmer 2-40, Walter 2-45)
Match report
Alastair Cook hit another century as Essex recovered from Jerome Taylor's early hat-trick to beat Sussex by 10 runs in the Royal London One-Day Cup.
Taylor ripped through Essex's top order to leave them 19 for three but Cook (109) and Ryan ten Doeschate (102) ensured Essex posted a competitive 295 for seven.
Chris Nash and Stiann van Zyl both scored half-centuries in Sussex's reply, while Jofra Archer hit 45 off just 22 deliveries, but Essex prevailed to move level on points with South Group leaders Somerset.
Cook took his total to 317 runs in five one-day innings with a second ton of the tournament, but it had looked bleak for Essex after Taylor had struck with the first three balls of his third over.
Varun Chopra chased a wide one to give Michael Burgess a diving catch behind for two, before Tom Westley fell to the same combination. And Adam Wheater was the hat-trick victim when trapped plumb lbw on the back-foot.
The fourth-wicket pair of Cook and Dan Lawrence set about repairing the damage. They put on 65 runs in 15 overs to take the score to 84 for four before Lawrence pushed a return catch to spinner Danny Briggs for 34.
That brought together Cook and Ten Doeschate, who shared a fifth-wicket stand of 142 with Ten Doeschate, who was run out off the last ball.
Ten Doeschate should have been out for 38 when he hit the ball almost vertically in the air, but Ajmal Shahzad put the chance down off his own bowling having raced to the striker's end.
Sussex were punished and, after Ten Doeschate passed 50, Cook swept a hip-high delivery from Shahzad for four to bring up a 122-ball century.
He was finally out when he cut Archer backward of square to Shahzad.
Ten Doeschate swatted a short delivery from Archer to reach his ton from the penultimate ball of the innings and was run out from the last having helped Essex add 99 in the last 10 overs.
In reply, Nash and Luke Wright shared a first-wicket stand of 67, but the ball after Wright had driven Jamie Porter for a straight six, he hooked straight to Paul Walter at deep fine leg for 32.
Nash and Van Zyl went 36 deliveries between boundaries, during which time they managed just nine singles, as they tried to set a platform.
Nash was eventually caught at mid on having made a 90-ball 66, before Van Zyl was dismissed for 61.
With seven wickets down and 54 runs required from less than six overs, it looked like game over.
But Sussex scored 21 runs off a nine-ball 45th over and, after Danny Briggs was bowled by Paul Walter, Archer smashed his second six of an entertaining knock.
However, Walter ended his fun five runs short of a 50 and then secured victory for his by bowling Taylor with 11 balls unused.