Surrey 298 for 7 beat Northamptonshire 296 for 7 by three wickets
Jason Roy and Chris Schofield both struck half-centuries as Surrey Lions went top of Group B of the Clydesdale Bank 40 with a three-wicket win over Northamptonshire Steelbacks at Wantage Road.
Alex Wakely made his best one-day score in crashing 94 off 77 balls - including seven fours and three sixes - as the Steelbacks posted 296 for 7, with captain Andrew Hall blasting an unbeaten 55 off 35 deliveries and Jade Dernbach taking 3 for 53.
Surrey reached their target despite a late wobble with seven balls to spare as Roy and Schofield made 65 and 72 respectively to end the hosts' hopes of a semi-final spot.
Northamptonshire won the toss and chose to bat but they lost David Willey for 23 in the fifth over when he smashed England international Dernbach to Zander de Bruyn at deep extra cover. Rob Newton then bludgeoned an explosive 42 off only 22 balls before launching de Bruyn to Zafar Ansari at mid-on.
Wakely reached 50 off 47 balls but David Sales walked on 28 when he was trapped leg before wicket by former England spinner Gareth Batty. Wakely was to fall six short of his first one-day century when he was superbly caught at long on by a diving Matthew Spriegel off Schofield.
Rob White was then run out for 38 by bowler Yasir Arafat before Dernbach bowled Steelbacks' wicketkeeper David Murphy for 2. James Middlebrook had made just one when he chipped Dernbach to Surrey captain Rory Hamilton-Brown at mid-off before Hall completed a half-century off just 33 balls in the final over.
Chasing 297, Hamilton-Brown crashed 46 off 30 balls before perishing by smashing Willey straight to Sales at cover. Fellow opener Davies blasted 42 off 29 deliveries before he went cheaply by slashing Willey high into the air and Hall took the catch at cover.
Roy then clattered his way to 50 off only 32 balls but he departed by chipping Paul Best to Sales at mid-on. Schofield then completed his half-century off 48 balls before Tom Maynard fell on 35 by launching Best to Wakely, who was standing at long off.
De Bruyn then followed for a duck by blasting David Lucas to Sales at extra cover and Schofield became Best's third victim when he was caught by Hall at mid-on. Spriegel then became the fourth batsman to be caught by Sales, this time at midwicket off Lucas, but a four through midwicket by Arafat off Hall sealed it for Surrey.