Gloucestershire 154 for 2 (Klinger 78, Marshall 42) beat Essex 153 for 8 (Westley 45) by eight wickets
Michael Klinger again proved to be Essex's nemesis as he guided Gloucestershire serenely to an eight-wicket win in the NatWest T20 Blast at Chelmsford.
The Australian rattled up two unbeaten T20 centuries against Essex last season, and added a third in the LV= County Championship for good measure.
Essex finally got their man here, but not before he had hammered 78 of the 132 runs scored while he was at the wicket.
With Hamish Marshall he put on 126 for the first wicket in 13.3 before the two men from Down Under, with a combined age of 72, departed in the space of four balls.
Marshall, who had earlier been dropped by James Foster when on one, was the first to go when he played on to Quinn for 42 off 34 balls.
And Klinger followed at the start of Wahab Riaz's first over from the River End when he edged a lifter through to wicketkeeper Foster. His imperious innings lasted 49 balls and included seven fours and four sixes. It condemned Essex to a fourth defeat in five T20 games this season.
Klinger had started Essex's agony when he won the toss on a slow track and scotched any hopes the home team might have had of another run chase by opting to bowl at them first.
That it wasn't going to be Essex's night was evident when Jesse Ryder went first ball, fishing outside off-stump to Matt Taylor to be caught behind by Gareth Roderick.
Tom Westley took up the attacking mantle, cracking Taylor through the covers, another through midwicket and turned Norwell backward of square for a third boundary.
Norwell's second over went for 13, but he might have had the wicket of Westley only for Andrew Tye to dive over a lofted drive at mid-on as it raced on for another four.
Tye was into the attack in the fifth over for his first spell since he was removed from the attack last Friday for bowling two beamers in the game against Glamorgan. His first over cost just three runs.
Krishen Velani, playing his first T20 in a year, and opening the innings, lifted an effortless six straight into the black sightscreen at the Hayes Close End off Norwell. But he was always the junior partner in a second-wicket stand of 46 before he chopped on to the same bowler for 16. Ravi Bopara was off the mark with a six, a push into the covers for two tripled by four overthrows. Westley hit a more conventional maximum, pulling Tom Smith over midwicket.
But having laid the foundations, Westley was deceived by a slower ball from Benny Howell and was bowled for his fourth forty in five T20 knocks this season. His 36-ball 46 included five fours and that six.
Ryan ten Doeschate followed soon after, run out for two by a direct throw from Chris Dent at mid-off after a review by the third umpire.
Dan Lawrence survived a caught-and-bowled attempt by Smith, and next ball Bopara top-edged the bowler over midwicket for six. But when Kieran Noema-Barnett replaced Smith at the River End, Bopara tapped his third ball tamely back into the bowler's hands to depart for 28.
The Essex mid-innings slump continued when Lawrence aimed to leg but lobbed up a dolly to Michael Klinger at silly mid-off to give Howell figures of two for 15. Essex were then 108 for six in the 16th over.
Ashar Zaidi livened up proceedings when he went after Noema-Barnett, hitting successive sixes over midwicket and cow corner. But having reached 17 off 10 balls, he fell to a slower ball from Tye.
Wahab Riaz took Essex to 150 in the last over when he hit Tye back over his head, but lost partner James Foster off the last ball, run out attempting a second run.
There was a rare occurrence at the start of the Gloucestershire reply when the usually infallible Foster failed to hang on to a chance high to his right when Hamish Marshall snicked Matt Quinn. The ball sped off the wicketkeeper's gloves and to the boundary for four.
Klinger continued his liking for the Essex bowling. The Australian straight-drove David Masters for six and also hooked Quinn for two sixes, the first when the ball was dug in very short.
Marshall, who was one when he received his reprieve, was scoring for much of the innings at the same rate as his partner, but only receiving half the number of balls. He, too, cleared the boundary ropes off Masters.
Klinger raced to his half-century off 32 balls with an ambled single of Zaidi, the fifty reached with four fours and three sixes.
The Gloucestershire captain added a fourth six, putting Lawrence over long-off before adding a boundary all along the ground to the same part of the ground.
Once the two openers had gone, Ian Cockbain and Dent eased Gloucestershire over the line with 19 balls to spare.