Surrey 279 for 9 (Sangakkara 130*, Roy 42) beat Northamptonshire 276 (Kleinveldt 76*, Cobb 66, Dernbach 4-39) by one wicket

Kumar Sangakkara's masterful 130 not out saw Surrey into the semi-finals of the Royal London Cup in a thrilling one-wicket win over Northamptonshire achieved off the last ball of the match.

With Surrey looking likely to crumble in a lower-order collapse, Sangakkara finally found a partner in No.11 Jade Dernbach and the pair found the 27 runs needed for victory.

Chasing 277, Surrey slid from 234 for 5 to 250 for 9 with two catches behind the wicket and two run outs as Sangakkkara looked on in frustration from the non-strker's end.

Twelve were needed from the final over and Sangakkara leapt across his stumps to paddle sweep Azharullah into the sightscreen for six over the wicketkeeper's head. It was an extraordinary shot at such a tense moment. Then with two to get from the final ball - although one would have brought Surrey victory by virtue of fewer wickets lost - he carved a boundary wide of point.

It left Northamptonshire heartbroken after a fine comeback in the field and Ben Duckett rueing his dropped catch of Sangakkara on just 7. It came straight to him, albeit firmly, in the gully. It was one a number of moments Northants were left to look back on with regret in the field in a match in which they conceded 13 wides and seven no balls.

David Ripley, Northants' coach, said: "I'm very proud of the effort but we made too many individual errors throughout the game - soft dismissals, catches went down, too many extras. But as a collective effort to fight our way back was phenomenal.

"With three overs to go we were favourites, so it's a double-whammy to have it taken away from us. Kumar was sensational in everything he did and it was a wonderful innings."

It appeared Surrey were cruising to victory after the chase swung their way in the 21st over. Richard Gleeson was brought back to bowl it. He pulled up with a side strain and left the field. Alex Wakely tried to finish the over but it proved a complete disaster with two high no-balls that were swung for six and four by Sangakkara. Another boundary saw 24 come off Wakely's four legal deliveries. It left 129 to get in 29 overs.

Sangakkara was composed and classy, working the bowling around and taking very few risks. A slog sweep against Graeme White brought him fifty in 61 balls. After flogging Wakely, he reached a third one-day century for Surrey in 116 balls. It did not seem then that it would take all of his experience to haul Surrey over the line.

Northants were bowled out for 276 with an over to spare - and their total looked light on a good batting surface. Josh Cobb gave them a steady start having lost the toss but regular wickets fell throughout the innings and the hosts were in danger of posting a total well below par without Rory Kleinveldt's fine late-order effort.

Kleinveldt's 76 in 62 balls gave the Northants innings a late revival. It was flagging at 227 for 9 but he found Azharullah for steady company and he blocked up an end to allow Kleinveldt to find the boundary. He carved Tom Curran wide of extra cover, and slapped a six over midwicket.

It followed Cobb's 66. He injected some life into the innings in the 19th over bowled by Gareth Batty. A straight drive beat mid-off for four, a waist-high full toss slapped over midwicket for another boundary and the subsequent free hit was launched far over long-on as 19 came from the over.

Cobb made his way to a smart half century in 54 balls but Tom Curran returned to angle a delivery into his middle-and-off stumps to break a stand with Alex Wakely worth 69. Wakely fell four overs later to a superb cutter from Sam Curran.

Cobb and Wakely began to move the Northants innings along after Jade Dernbach claimed two early and very important wickets, both of them bowled to the batsman's strengths. A ball on the pads of Richard Levi was flicked into the hands of James Burke at deep square leg; another outside off stump to Ben Duckett was slapped to cover diving forward, Burke again the catcher. Dernbach returned to finish the innings off and claim 4 for 39.