Gareth Rees slammed a century as Glamorgan earned their first win in the Clydesdale Bank 40 with a 29-run victory over Lancashire on the Duckworth-Lewis method.
Opening batsman Rees finished unbeaten on 110 from 103 balls, including nine fours and three sixes, in a total of 231-5 after the visitors chose to bat first at Old Trafford.
He received good support from Alviro Petersen (44) and Jim Allenby (30), while Lancashire spinner Stephen Parry picked up 3-46.
Rain meant Lancashire were initially left to chase a revised target of 229 in 39 overs and all seemed to be going well during a second-wicket stand of 91 between Karl Brown (48) and Stephen Croft (52).
But they lost four wickets in a crucial five-over spell, leaving them behind on D/L and, after heavy rain forced them off the field at 125-5 and prompted another revision, they returned needing 48 off three overs.
And Glamorgan held their nerve as Lancashire finished on 143-7 from 28 overs, seam trio Will Owen (3-24), James Harris (2-33) and Allenby (2-26) sharing the wickets to fall.