Stewart Walters' classy knock ensured Surrey picked up their second only win in Pro40 Division Two against Northants at the Brit Oval.
Walters finished on 91 off 83 balls, his best ever limited-overs score, in a total of 268 for six.
He then snapped up three vital catches as the Brown Caps comfortably ran out winners by 63 runs with four overs to spare, despite a Riki Wessels century.
Matt Nicholson took two wickets as the Steelbacks suffered early on (7-3).
In between Nicholson's strikes (Stephen Peters and Rob White, both for ducks), Niall O'Brien was trapped leg before wicket by Jade Dernbach for five.
The visitors did recover to 114 for three courtesy of a century stand between Wessels and David Sales before Sales holed out to Walters at deep point for 38 in the 19th over.
In the next over, Lance Klusener chopped onto his stumps without scoring.
Debutant Robert Frylinck picked his first scalp with the dismissal of Johan van der Wath for seven and followed that up with the prized wicket of Wessels, who after completing his century from 85 balls holed out to deep mid-wicket.
Having been put into bat, Surrey were soon in trouble when they lost opener Scott Newman for six in the second over.
The Brown Caps then rallied as James Benning and Walters shared an 89-run partnership for the second wicket - but that was eventually broken with the score on 100 in the 16th over.
Benning had advanced to 55 when he was surprised by a ball from Hall that kept low and gave a simple catch to O'Brien behind the stumps off a bottom edge.
Afzaal made his intentions clear with an immediate boundary but after scoring a quick-fire 23 he was clean bowled by Nicky Boje.
Walters went to his half-century in just 55 balls and added a further 72 runs for the fourth wicket with Jonathan Batty who fell in the 34th over to the returning Johann Louw.
But Walters fell nine short of his century when he was beaten by some late turn from Brown, and Nicholson was run out for 13 in the penultimate over after a mix-up with Mark Ramprakash who was undefeated on 36.
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