Essex maintained their hopes of reaching the semi-finals of the Yorkshire Bank 40 after crushing Durham by six wickets by Chelmsford.
The hosts got home with 13.3 overs to spare, successfully chasing down Durham's meagre 138 all out.
Ryan ten Doeschate and Ravi Bopara made light of the task with a fourth-wicket partnership of 94 in 18 overs before the latter departed for 38. Ten Doeschate completed his side's emphatic victory with an unbeaten 74 spanning 64 balls and featuring two sixes and eight fours.
The visitors started the match at the head of Group B but struggled against a wonderful exhibition of pace bowling from Graham Napier.
The Essex all-rounder took five for 21, including a devastating spell of four wickets for one run in 2.2 overs at the start of the innings, as Durham sank to nine for four after 4.2 overs.
Mark Stoneman, Scott Borthwick and Paul Collingwood all failed to score as Napier ran amok. He removed Stoneman with his second delivery of the match and three balls later found an edge as Borthwick pushed forward to give James Foster one of his three catches.
Former England star Collingwood failed to dig out a yorker while Phil Mustard reached just nine before he became another Napier casualty.
Will Smith made a gallant effort to sustain the innings with a 73-ball half-century that included five boundaries, and he found useful support from Gareth Breese with the pair adding 55 in 11 overs for the seventh wicket.
Breese was bowled by Ten Doeschate and soon after Smith drove Tymal Mills to Bopara at mid-off as Durham's innings ending as ignominiously as it had started with the loss of three wickets for one run.
Bowled out in 34.1 overs, the visitors did have some early impetus when Essex started their reply as they captured three wickets for 30 runs in 11 overs.
Hamish Rutherford edged Mark Wood to slip in the first over, Mark Pettini was pinned in front of his stumps by Chris Rushworth three overs later and Greg Smith played down the wrong line and was bowled by Wood.
But Bopara and Ten Doeschate soon steadied matters as they composed their match-winning stand.
When Bopara became a second victim for Rushworth, only 15 more runs were required and Ten Doeschate duly completed the win to send Essex into Twenty20 Finals day on Saturday in good heart.