Simon Katich hit a match-winning 57 from 37 balls to lead Lancashire to a five-wicket Yorkshire Bank 40 win over Surrey at Guildford.
When Gareth Cross, who contributed an unbeaten 24 off 15 balls, joined his captain in the middle, the visitors needed 76 in nine overs for their Group B victory.
But Katich breezed to an unbeaten half-century to see his side to their victory target of 265 with 15 balls to spare.
Jason Roy (50) and Steven Davies (53) had earlier laid the foundations for what should have been a mammoth Surrey total by putting on 101 for the first wicket.
Davies hit three sixes en route to a 26-ball half-century, as Surrey raced to 100 without loss inside 12 overs and would have had a fourth maximum had it not been for an excellent catch on the midwicket boundary by Stephen Moore.
Roy moved to a run-a-ball fifty before backing away and toe-ending an attempted cut off Jordan Clark through to the wicketkeeper.
Surrey lost regular wickets throughout the remainder of the innings - including two each for Kyle Hogg and Jordan Clarke - before Zander de Bruyn's 34 not out saw them up to 264-8.
In reply, Lancashire were handed a decent start by Ashwell Prince and Stephen Moore. Prince, who launched Ansari for a straight six, reached his fifty in 43 deliveries, but not before Jon Lewis had struck with 85 on the board by having Moore caught off a leading edge for 30.
Prince and Croft combined for a further 55 in nine overs before Croft (25) was caught behind off Dernbach.
The turning point appeared to come when Azhar Mahmood had Prince caught at mid-off for 76 and Brown chopping on next ball.
But Clark kept the visitors in the hunt by hitting 27 in as many deliveries before handing the baton to Katich.