Essex 166 for 5 (Pettini 42, ten Doeschate 40*) beat Surrey 165 for 4 (Wilson 63*) by five wickets
A near-faultless Essex side moved one step closer to a home quarter-final with a sixth consecutive victory in the South Group. Few sides will relish visiting Chelmsford should it come to pass and Surrey, especially Kevin Pietersen, found the atmosphere more hostile than most as their own winning run came to grief.
Surrey's explosive top-order - minus Tillakaratne Dilshan, who has left for international duty - failed to ignite for the first time in this campaign and after a false start, their total of 165, on a flat track with short boundaries, was also going to require miracles in the field to defend.
Alas for Surrey, they could not subdue the polished Essex order or indeed the partisan crowd. Pietersen was booed, and noticeably rusty, and his tribulations embodied Surrey's undercooked performance. Having lost to Essex at the start of June in the corresponding fixture, Graham Ford's side have scarcely been stretched either with the bat or ball since and that showed.
Pietersen had laid his cards on the table, stating he hasn't given up on playing for England again. On this evidence, however, he would struggle to even attract the slightest interest of the selectors regardless of the politics involved.
True, he has had to feed off scraps during his weekly Blast session (although on this occasion he played against Kent on Wednesday as well) but the limited outings are having a conspicuously detrimental effect on his batting. His rustiness was discernible from the moment he walked to the crease.
Without facing a delivery, he was down and by all accounts out. Pietersen couldn't evade a Jason Roy rocket at the non-striker's end and was impaired by the blow to his midriff. His 11-ball stay ended in apt fashion, as he walked past one that slid down the legside.
The welcome he got from the Chelmsford faithful - boos mixed with chants of "England" - will have bothered him little but the nature of his grim effort couldn't be masked. A flick into the leg side of Graham Napier preceded eight consecutive dot balls to the left-arm spin of Tim Phillips.
Surrey couldn't find the same unrelenting consistency with their bowling. After Azhar Mahmood removed Jesse Ryder in the opening over of the run chase, their usually reliable gameplan unravelled. Tom Westley cracked seven boundaries, predominantly through the leg side, and Mark Pettini, on his way to 42, did not give the bowlers a moment's peace as Essex rattled along with ease.
Kevin O'Brien struck to have Westley trapped in front to stem the flow temporarily and when Matt Dunn took two wickets in the 15th over - that of Ravi Bopara and Pettini - Surrey threatened to silence the crowd. But, Essex's strength in depth is striking and Ryan ten Doeschate eased any nerves by clubbing two fours and a six to get his side across the line with minimal fuss and nine balls remaining.
It was, however, Surrey's failings with the bat that cost them. Much like Pietersen received a working over by Phillips, the Surrey physio was overburdened too. Roy had just ignited a faltering innings by launching Matt Salisbury over the stand at the River End but never recovered from a nasty blow to his foot from Napier's inswinger.
Such have been Roy's exploits at the top of the order, Surrey's middle-order have rarely been called upon. But Essex fell into the trap of taking their foot of the pedal after they saw the back of Roy - bowled by Bopara for a scratchy 29 - as they discounted Surrey's strength thereafter.
In Wilson they have a steadfast performer who attracts very little attention amidst a changing room of stars. The Chelmsford crowd certainly knew all about him by the time he had put on 72 in seven overs with Ireland compatriot O'Brien to give Surrey a chance. It was never going to be enough, however.
As ten Doeschate and Foster scampered the winning run, the PA announcer wasted little time in trumpeting the fact Essex are top of the division. Indeed they are, and sitting pretty too.