Surrey 155 for 6 (Sangakkara 34, Roy 33,) beat Gloucestershire 154 for 5 (Handscomb 39, Jones 37*, Dunn 2-15) by 4 wickets
The hottest day of the year produced a blistering finish for a sell-out 23,000 crowd at the Kia Oval when Surrey veteran Azhar Mahmood swung the last ball of the match over deep square leg for six to earn his side a dramatic NatWest T20 Blast victory against Gloucestershire by four wickets.
Craig Miles, the highly-promising 20-year-old Gloucestershire fast bowler, was inconsolable as 40-year-old former Pakistan all-rounder Mahmood proved equal to the challenge of needing to hit the final ball of the match over the ropes to take Surrey past their visitors' 154 for 5.
Mahmood said: "I knew when I connected that it would be six. I had missed the previous ball, which was also short, and I thought the last one would also be short. There was a bit of a delay between the last two balls, as they discussed with the bowler what he was to do, and that helped me because I had a little bit more time to get myself calm and collected."
Michael Klinger, Gloucestershire's captain, defended his bowler. "Craig bowled a fantastic last over to get them from wanting nine off six balls to six from the last ball. He also executed exactly what we asked him to do with that last ball - so there's no blame on him. We had three young guys bowling the three last death overs, and because of injuries they have had to step up into those roles. It is not easy, and they put in a pretty decent effort."
Mahmood ended 22 not out from 14 balls, with two sixes and a four, after also straight driving for six the second ball he faced, from slow left-armer Tom Smith: and how Surrey needed his late heroics.
Gloucestershire will blame themselves, though, for losing a game which - at the death - they looked like snatching. Miles had dismissed Zafar Ansari to a catch at fine leg in a good last over, the final ball apart, but he also began it with a wide - when Surrey needed nine runs from the last six balls - and, in all, Gloucestershire's bowlers sent down nine wides and two no balls in the closing overs.
Kieran Noema-Barnett was particularly guilty, bowling four wides in the 14th over when he repeatedly tried, and failed, to bowl yorkers a couple of feet outside off stump, and Benny Howell bowled two wides and an overstepping no ball, leading to a free hit, in the 19th over.
Surrey, despite Kumar Sangakkara leading the chase with 34 from 33 balls, still needed 45 from the last five overs, 40 from four, 30 from three, and then 20 from two before Howell needlessly gave away extra runs.
Sangakkara was caught at deep mid wicket in the 17th over, soon after Ben Foakes had also been caught on the boundary for 27, and Gloucestershire's two spinners were excellent with Smith taking 2 for 24 and off spinner Jack Taylor 1 for 22.
Earlier Jason Roy had threatened to speed Surrey to their target with a 17-ball 33, with a six and five fours, but he was smartly stumped when he was drawn forward and beaten by Smith's flight and turn.
Four Gloucestershire batsmen got into the 30s, but none of them could play the major innings their team wanted as a slow, turning pitch mitigated against explosive shot-making on what is a traditionally fast-scoring ground.
Hamish Marshall and Ian Cockbain hit 32 and 31 respectively in the early overs, while the best partnership of the innings was 62 in eight overs for the fifth wicket between Peter Handscomb, who top-scored with 39 but never really threatened to take the game away from Surrey, and Geraint Jones, unbeaten on 37.
Spinners Gareth Batty, with 1 for 20 from his four overs, and Ansari, who took 1 for 27 from his four-over allocation, were the pick of Surrey's bowlers.
Cockbain and Marshall had added 46 in just over five overs after Michael Klinger, on 2, had hit Matt Dunn to mid off from the eighth ball of the match.Cockbain inside-edged a pull at Dunn on to his stumps one ball after swatting him for six over deep mid wicket. Likewise, Marshall fell immediately after pulling Ansari over mid wicket for six - beaten by a ball which gripped and turned, which he edged into wicketkeeper Gary Wilson's gloves.
Benny Howell made just a single before reverse-sweeping Batty's off spin to point in the 10th over, and it was left to Handscomb and Jones to try to get Gloucestershire up to a defendable total.
Handscomb, however, hit just three fours in his 39 from 36 balls and former England wicketkeeper Jones battled on bravely to 37 not out from 31 balls despite needing treatment for a heavy blow in the box when he was pinned by Tom Curran.