Glamorgan 195 for 6 (Carlson 58, Wagg 46*, Meschede 43) beat Surrey 194 for 4 (Maddinson 70) by four wickets
Glamorgan revived their hopes of reaching the knockout stages of the Vitality Blast after chasing down 195 with six balls to spare to beat Surrey by four wickets at the Kia Oval.
They lost openers Aneurin Donald and Usman Khawaja with only 15 runs on the board, but Craig Meschede's 43 off 19 balls got them back on track before Kiran Carlson and Graham Wagg provided further acceleration in a fifth-wicket stand worth 59 from 31 deliveries.
Carlson hit five fours and four sixes in 58 from 32 deliveries and although he drove Rikki Clarke's slower ball to mid-off in the 15th over, he left his side needing 39 from five overs and Wagg made sure there were no further alarms, finishing unbeaten on 46 from 26 balls having earlier bowled four accurate overs at a cost of just 21 runs.
Victory continued Glamorgan's outstanding T20 record at The Oval. It was their sixth win in seven visits and made even better by the absence of captain Colin Ingram, who was ill, and Australian Joe Burns through injury.
"I'm incredibly proud of everyone, that was a great run chase," stand-in captain Chris Cooke said. "We lost Joe Burns yesterday and Colin Ingram today and I only found out I would be captain on the bus coming here but it was a triumph out of adversity and just a really good win for us."
It was a blow for Surrey who would have gone top had they won - an outcome that seemed likely at halfway after Nic Maddinson's 70 has helped them to 194 for 4 on a surface being used for the second time after Surrey Stars had played Lancashire Thunder in the Kia Super League earlier in the day.
Glamorgan would have been relatively pleased to remove Surrey's explosive openers Aaron Finch and Jason Roy in successive overs to leave the hosts 58 for 2 in the seventh. Finch slapped a long hop to extra cover in the sixth over and Roy, whose 27 included two sixes, failed to clear long on in off-spinner Andrew Salter's first over.
But Maddinson, whose previous three innings in his debut campaign in the Blast had brought him a modest 39 runs, made his 10th half-century in the format before he was run out in the final over, having hit three sixes and five fours from 45 balls faced. The 26-year-old added 57 in 6.3 overs with Ben Foakes for the third wicket before Ollie Pope joined him to put on 71 off 37 balls.
Maddinson had a life on 31 when Wagg dropped a simple return catch in his follow-through before he had Foakes well caught by Selman running back from long on later in the same over.
Pope twice cleared the ropes as Surrey scored 57 from the final five overs and Glamorgan looked to be up against it when they lost both openers in the first three overs of their reply. Donald flicked Jade Dernbach to short fine-leg then Khawaja was well taken at mid-on by Gareth Batty off Tom Curran.
But Meschede revived their hopes by hitting Batty's first three balls for six before he was caught at short third-man off the fourth.
Acting skipper Cooke was caught at long leg off Scott Borthwick and at halfway Glamorgan needed 101 but Wagg deposited three successive balls from Borthwick into the stands and from then on his team always looked favourites.
Wagg and Selman took them to within 12 runs of their target and although Selman drove Curran's slower ball to mid-off, Salter swung the winning runs into the leg side off the final ball of the penultimate over to secure Glamorgan their third win of the tournament so far.