Tom Westley smashed a brilliant century before five wickets from Jesse Ryder took Essex Eagles into the NatWest T20 Blast quarter-finals.
Kent Spitfires were well beaten as the home side began the Colchester Festival in style at Castle Park.
With Essex having won eight games batting second so far this season - and lost the only time they batted first - it was probably of little surprise that Kent skipper Rob Key asked the hosts to bat first when he won the toss.
And it looked like an inspired decision as the Eagles were soon in all sorts of bother.
Mark Pettini fell without score to the second ball of the match, edging Darren Stevens to slip.
And when Mitchell Claydon had Ryder caught behind off the first ball he bowled, the home side were 2-2 in the second over.
But Westley and Ravi Bopara rebuilt with a partnership of 92 in 11.3 overs, before the England man fell for 23 from 23 balls - a knock which contained just one four.
But at the other end, Westley was more than enjoying himself, and he smashed 10 fours and six sixes in his 105, which anchored the innings.
Essex stuttered slightly once he was out with the score on 166, with the next two overs worth just 11 runs.
But then skipper Ryan ten Doeschate came to the fore, whacking 32 in a brutal final over, including four sixes, as his side closed on 209-5, with his dismissal from the last ball of Ben Harmison's torrid over seeing him out for 37 from 15 balls, with James Foster unbeaten on 36 from 21.
Daniel Bell-Drummond hit the first ball of Kent's reply for four, but was walking back to the pavilion after the next, nicking hometown hero Graham Napier to Foster.
Key made just one from three balls before being bowled by Matt Salisbury, and when Fabian Cowdrey was out trying to scoop later in the over, the Spitfires were 21-3.
Sam Northeast (41) and Alex Blake (29) tried to revive the innings and put on 40, before Ryder came to the party, having Blake caught by Greg Smith.
Stevens made 19 before falling to Tim Phillips, and when Northeast fell, stumped off the same bowler, Kent were 102-6 in the 12th over.
Sam Billings made 25, but he fell off the first ball of the 14th over to Ryder, who then took two in two later in the over to leave Kent staring down the barrel.
Harmison was unbeaten on 18 at the end, but Ryder wrapped things up with his fifth wicket, Adam Riley the victim, as Essex won by 63 runs in the 16th over.
The Eagles are now four points clear at the top of the table with two games in hand on Hampshire.
One more win will guarantee a home tie in the last eight as the Eagles look to reach Finals Day for the second year running.
