Surrey 557 (Pietersen 355, Raine 4-124) and 218-3 (Davies 115*, Roy 67) beat Leicestershire 292 (Lewis 126, Raine 57, Dunn 4-72) and 480 (Eckersley 118, O'Brien 78, Robson 55, Ansari 6-152) by seven wickets
Kevin Pietersen was able to watch delightedly from a Surrey dressing room that has given him unstinting support as Steven Davies and Jason Roy spearheaded a startling seven-wicket Division Two victory against shell-shocked Leicestershire at the Kia Oval.
Davies reached a superb hundred off only 57 balls, finishing with 115 not out from 69 balls with four sixes and eleven fours.
Needing 216 from 24 overs after finally finishing off a resilient Leicestershire second innings for 480 in the fifth over after tea, Surrey romped home with 16 balls to spare on the back of a thrilling assault by Davies and Roy, who flayed 67 from 39 balls.
Kumar Sangakkara then came in to hit his first two balls for four and although he fell for 12 it hardly slowed the Surrey chase with Gary Wilson and then Rory Burns helping Davies to propel Surrey to their victory target.
Although it was Pietersen's epic first innings 355 not out that had put Surrey into a winning position at the halfway mark, his strokeplay was not needed second time around as Roy and Davies launched themselves at the Leicestershire bowling to put on 145 for the first wicket in just 11.1 overs.
Sixes and fours flew from their flashing blades and Roy and Davies brought up Surrey's 50 in the fifth over and the 100 in the eighth. At the ten-over mark Surrey were 133 without loss and victory was all but assured when Roy was caught on the cover boundary in the 12th over after hitting four sixes and six fours.
The excellent Oval batting pitch, which had earlier so frustrated Surrey when they were trying to winkle out the last five Leicestershire wickets, now gave the visiting bowlers little chance of containing Surrey's destructive top three - especially with a short boundary on one side of the ground.
Davies completed his fifty from just 24 balls - four balls less than it had taken Roy - and the left-hander displayed all the flair which has won him 13 limited-overs international appearances for England in a career which has stalled somewhat in recent years.
Surrey's first championship win of the season earned them a maximum 24 points, while Leicestershire took just five points for what is their 20th defeat in 36 win-less championship games since September 2012.
And yet Leicestershire came so close to denying Surrey on a final day which, until the dramatic and thrilling finish, had seemed increasingly certain to end in a draw. This defeat will hurt them badly, because at tea - when they were 470 for 8 - they must have thought they had done enough to keep Surrey's bowlers at bay.
But Jigar Naik, who had batted for 102 minutes for 30, was caught at slip off Gareth Batty's off spin and then, five balls later, Rob Taylor - his partner in a ninth wicket stand that had brought 62 in 28 overs of defiance - edged Zafar Ansari to keeper Gary Wilson after scoring 42 from 119 balls in two and a half hours.
Ansari, the 23-year-old whose slow left-arm spin is rapidly improving, took a career-best 6 for 152 from 51.1 overs of hard toil. Ansari and Batty, who took 2 for 100 from 46 overs, bore the brunt of the bowling responsibilities in the absence through injury of fast bowler Chris Tremlett, who could only send down seven overs in Leicestershire's long second innings.
The day began with Leicestershire only 45 runs ahead on 310 for 5 but Niall O'Brien turned his overnight 38 into a fighting 78, from 178 balls, and although he lost Ben Raine in the 11th over of the morning, leg-before to Ansari, he immediately found another stubborn partner in Clint McKay.
Raine's 33 had helped O'Brien to add 72 for the sixth wicket, and 51 more runs came in alliance with McKay before O'Brien drove Tom Curran straight to short extra cover.
McKay batted almost two hours for 41, and when he was leg-before to Ansari it seemed as if Taylor and Naik would be equal to the task of guiding Leicestershire to safety. It was not to be, however, and Pietersen, who did not field all day because of a calf strain which required a scan, could at least celebrate a Surrey victory in what might yet be his last first-class match.