Surrey 137 for 7 (Pietersen 39, Waller 2-24) beat Somerset 136 for 9 (Trego 30, Dunn 3-8) by three wickets

The scrimmage for the quarter-final berths in the ultra-competitive South Group is becoming increasingly fraught. Having coasted into a position of influence, Surrey's hopes of advancing had suffered a setback of late but Kevin Pietersen played his most significant hand to date with an assured cameo to ensure his side were on the right side of the fine margins this time around. They are now within touching distance of the knock-out stages.

If things had been different, Pietersen would have been across the other side of the capital resting up on the eve of a Test match. As it was, he - for the first time this season - showed why many regard the ECB's decision to discard him as risible. Two trademark cover drives had the crowd purring and Surrey motoring in pursuit of Somerset's 136 for 9.

But his dismissal, succumbing to spin on a surface conducive to slow, take-all-the-pace-off bowling for 39, opened a window of opportunity for the visitors. But, unlike Surrey's astute operators, Somerset weren't able to apply the stranglehold to induce a middle-order wobble.

Pietersen powerfully cut Max Waller to the boundary first ball of the tenth over but fell next delivery, attempting to replicate the stroke. When Robin Peterson haphazardly ran himself out in comical circumstances after a mix-up with Azhar Mahmood, a tense silence engulfed a sold-out Oval as another edgy finale loomed.

But, with the equation set at ten required off two overs, Somerset were up against it and a couple of lusty blows from Chris Tremlett was enough. Had Marcus Trescothick - playing as a makeshift wicketkeeper in the absence of Craig Kieswetter - been able to throw down middle stump or Colin Ingram manage to scamper around from long-on to snaffle Mahmood in the final overs, things may have finished differently - but such are the fine margins in the shortest format.

A two-wicket victory with a couple of deliveries to spare all but ends Somerset's hopes of finishing in the top four but ensures there is a realistic chance of another sell-out crowd at The Oval this season. True, there was no Jason Roy fireworks - he fell for just 4 in the first over - and a two-paced surface didn't allow flamboyant strokeplay but that suited the hosts.

Gary Wilson hardly had to affirm the inevitable when the coin landed in his favour but that alone doesn't guarantee his bowlers will execute the gameplan. Successive defeats hinted that their dependable strategy was unravelling.

Glamorgan's thrilling victory here five days ago apart, the team chasing at The Oval in the last ten domestic Twenty20 games had come away with the points and the hosts ensured Friday's blip in the trend was just that. True, they were aided by a surface fabricated to suit their strengths but isn't that what home advantage is about?

While it would be easy for Wilson to turn to his slower bowlers to roll their fingers over the ball on a two-paced surface for all 20 overs, he placed just as much faith in his battery of seamers. Matthew Dunn is another promising cab off the Surrey ranks and highlights that there is more to the club that meets the eye of many. An inspired spell of 3 for 8 proved decisive and enough for him to earn the plaudits.

Having being crashed to the fence first ball by Nick Compton, he stuck to his guns, bowling fast and full and was duly rewarded. Just as the visitors were beginning to motor, Compton played an atypically ugly heave to be caught at point. It was a needless shot as Somerset raced along at close to ten an over during the Powerplay.

To that point, he had crunched and punched four boundaries in quick succession as he took Tillakartne Dilshan for 13 in the first over; that was the last we saw of the Sri Lankan with the ball. But, Somerset were unable to attune themselves to the pitch and Surrey's astute methods. Their innings became stagnant fairly quickly after a brisk start.

By the time Dunn returned to bowl the penultimate over, the wheels had come off the innings. He The quashed any hopes of a late burst as James Hildreth was caught by Zafar Ansari and next delivery, he exhibited his unerringly accurate yorker - it was far too good for Tim Groenewald. Alas, the hat trick ball was safely negotiated by Waller. but Dunn had already inflicted the damage.