Surrey 273 for 9 beat Northamptonshire 261 for 9 by 12 runs
Surrey maintained their unbeaten record in Clydesdale Bank 40 Group B with a dramatic 12-run victory over Northamptonshire under the lights at the Oval.
In what proved to be a high-scoring contest full of twists and turns, Surrey captain Rory Hamilton-Brown came to the fore in the closing overs to halt the Steelbacks' charge towards a victory target of 274 by claiming three crucial wickets in the space of eight balls.
Hamilton-Brown (3 for 38) dismissed Rob White, Alex Wakely and Andrew Hall to reduce their opponents from a healthy-looking 232 for 3 to 244 for 6, and the visitors never recovered as they finished on 261 for 9.
Northamptonshire were handed an excellent start in their run chase by opening duo Mal Loye and David Willey, who combined for 138 in 21 overs. Willey, who was pushed up the order to open after Stephen Peters pulled a calf muscle in the field, struck a career-best 74 off 79 deliveries, which included seven fours and a six straight down the ground off Tim Linley.
At the other end, Loye, who has struggled for form in this season's CB40, powered his way to 63 off 65 deliveries. Willey's maiden one-day half-century, which came off 43 balls, arrived in the 15th over, shortly after Loye had brought up the hundred partnership with a maximum off Zafar Ansari.
Gareth Batty then pegged the visitors back with two wickets in seven deliveries, first having Loye caught at deep midwicket and then dismissing Niall O'Brien caught and bowled for three. Willey departed four overs later when he slapped Yasir Arafat to midwicket.
That left the visitors on 164 for 3 but Wakely, who struck three boundaries and two sixes in his 32-ball knock, and White helped turn the contest back in Northamptonshire's favour with a blistering fourth-wicket stand of 68 in seven overs.
However, with victory seemingly within their sights, Hamilton-Brown made his treble breakthrough to end Northamptonshire hopes and help leave Surrey at the top of Group B with seven wins from eight games.
Earlier, Surrey, who were without Mark Ramprakash after he was banned by his club for showing ''serious dissent'' at an umpiring decision during last weekend's County Championship victory over Gloucestershire, started watchfully before their opening duo of Hamilton-Brown and Steve Davies plundered 54 runs from four overs.
That left the home side on 60 without loss in the seventh over, but the introduction of Hall helped Northamptonshire battle back. He made the first breakthrough, bowling Hamilton-Brown for a 31-ball 43, and then two overs later accounted for Jason Roy with a similar delivery.
However, Davies and Tom Maynard then settled in to a stand of 99 in 14 overs for the third wicket to take Surrey up to 171 for 2. Having survived a caught and bowled chance on 31, Davies moved to his half-century in 48 balls and brought up the fifty partnership with four through extra cover off James Middlebrook.
Davies, who was dropped again when on 61, eventually perished in the 24th over when he was bowled backing away to Middlebrook's off-spin. The 25-year-old left-hander had hit 78 off 68 balls, including 11 fours. Five overs later, Maynard picked out Lucas at deep backward square leg off the bowling of Paul Best, though not before posting a 45-ball half-century.
In the first over of the batting powerplay, Matthew Spriegel (38) launched Hall over long-on for six, but Surrey lost wickets attempting to accelerate towards a bigger total, slipping from 247 for 4 to 273 for 9 in the space of five overs, Hall finishing with figures of 4 for 44.