Ravi Bopara struck 115 not out as Essex swept to a seven-wicket victory over Surrey in their Yorkshire Bank 40 Group B clash.
Bopara's 94-ball innings, assisted by 65 from Greg Smith, ensured the visitors chased down Surrey's 223-7 with 4.5 overs to spare for a fifth victory in eight matches.
Bopara and Smith came together at 15-2, after Mark Pettini had been caught at cover for five and Hamish Rutherford athletically held at the wicket on nine, and their stand of 152 in 25.3 overs was a perfect demonstration of controlled acceleration.
It was also an Essex third-wicket record against Surrey in all List A one-day cricket, and when Smith skied his 77th ball, from Jon Lewis, to deep mid on in search of his fourth six it merely signalled a final onslaught from Bopara and Ryan ten Doeschate, who added a further 59 in a mere 4.3 overs.
Bopara reached his 90-ball century during a 34th over, bowled by Zafar Ansari, that cost the left-arm spinner 21 runs. Both Bopara and Ten Doeschate hit a six and a four in the over, and the end came soon afterwards.
Surrey, with virtually no chance of qualification for the semi-finals next month, opted to play a youthful team and rested key one-day players Jade Dernbach, Azhar Mahmood, Gareth Batty and Steven Davies ahead of Tuesday's Friends Life t20 quarter-final against Somerset.
One of two teenagers given a senior debut, 17-year-old batsman Dominic Sibley, had a game to remember for the wrong reason after being stretchered off with a badly cut knee early in the game.
Sibley, still at Whitgift School, suffered a two inch deep gash as he dived for the crease to avoid being run out during the fourth over of Surrey's innings.
After completing another single when partner Vikram Solanki called him for a run several balls later, he signalled to the dressing room that something was badly wrong.
Solanki went on to top-score for Surrey with 86 from 95 balls, with ten fours, before being bowled swinging at Reece Topley at the start of the 35th over.
Tom Curran, the 18-year-old son of former Zimbabwe all-rounder Kevin Curran and Surrey's other debutant, was run out second ball for one by Bopara's direct hit from mid off.