Glamorgan 186 for 7 (Northeast 63*, Thomas 2-23, Ogborne 2-36) beat Somerset 171 for 6 (Umeed 45, Dickson 44, Kellaway 2-37) by 15 runs
The last leg of Somerset's treble bid went the way of the first two as Glamorgan won a truncated Metro Bank One-Day Cup Final on a gloomy reserve day at Trent Bridge that mercifully stayed dry long enough for them to lift the trophy for the second time in four years.
In a match reduced in advance to 20-overs a side after Sunday's total washout, overhauling Glamorgan's 186 for 7 proved beyond them as the Welsh county, who beat Durham here to win the 50-over competition in 2021, came out on top by 15 runs, restricting Somerset to 171 for 6.
Sam Northeast had anchored the Glamorgan innings with an unbeaten 63, while Billy Root added 39 off 27 balls, both hitting two sixes in a crucial fifth-wicket stand, Timm van der Gugten backing them up with 26 off just nine balls to bookend Will Smale's 28 from 14 at the top of the innings.
Skipper Sean Dickson hammered 44 from just 20 balls after Andy Umeed's 45 from 36 for Somerset, but after offspinner Ben Kellaway and seamer Andy Gorvin had taken two wickets each, Glamorgan's Jamie Mcilroy and Dan Douthwaite held their nerve with two fine overs at the death to finish the job.
Beaten in the Vitality Blast final and knocked out of the race for the Vitality County Championship in the preceding nine days, the defeat left Somerset empty handed yet again.
The only disappointment for the winning team was that their moment of triumph was witnessed in the flesh by only a smattering of spectators on the ground rather than the thousands who had turned up on Sunday.
England spinner Jack Leach did not bowl a ball as Somerset opted to rely on five seamers, of whom George Thomas took 2 for 23 and left-armer Alfie Ogborn 2 for 36 from their four-over allocations.
After Sunday's total washout forced the teams to return for the scheduled reserve day, play mercifully began on time, with the contest sensibly reduced to 20 overs per side even before the toss had been made, in anticipation of more heavy rain due to arrive in early afternoon.
Somerset won the toss and opted to bowl as the Trent Bridge floodlights illuminated the misty gloom hanging over the ground.
Ogborne took wickets with his third and fourth deliveries, bowling skipper Kiran Carlson before Tom Bevan shovelled tamely to short fine leg, but Glamorgan still put up 39 runs in the first four-over powerplay thanks to Smale's aggression.
Smale raced to 28 from his first 13 balls, living dangerously against Josh Davey with three boundaries over third but striking Ogborne cleanly over mid-on and for six over square leg. The threat he posed was removed when Dickson held a brilliant catch falling backwards at mid-off.
After South African Colin Ingram, one of Glamorgan's trump cards, picked out wide long-on off Thomas for just 11, Glamorgan were 71 for 4 from 10 and needed to find new energy.
It came initially from Root, who cleared the rope three times, with Northeast eventually following suit with two of his own, one from a free hit, as Kasey Aldridge's final over went for a damaging 29. They added 78 in 49 balls before Root was caught behind off Thomas.
The next two wickets came quickly as Northeast's failure to run as he was caught off a no-ball left the big-hitter Douthwaite stranded, before Kellaway sliced to short third, but van der Gugten's swashbuckling cameo, encompassing four fours and a six off Davey hammered over long-off raised the total to something that looked defendable on a slow pitch.
In reply, Somerset had Thomas run out in the third over of a stodgy powerplay and were some way off the pace at 63 for 2 from 10 after Lewis Goldsworthy, who had hit a century in the semi-final to down holders Leicestershire, picked out long-on off Kellaway, although Umeed was beginning to land some blows.
A double setback followed as Umeed fell to a superb catch by Smale standing up to Andy Gorvin and James Rew was caught off a top-edged sweep as Kellaway landed his second blow, leaving Somerset 89 for 4 in the 13th and Glamorgan firm favourites.
A blistering partnership of 66 in just five overs between Dickson and Archie Vaughan dragged Somerset right back into contention, Vaughan having survived Kellaway's lbw shout on umpire's call before he had scored.
But after hammering 44 from 20 balls, hitting sixes off van der Gugten (twice) and McIlroy, Dickson reversed Gorvin to short third - from a delivery that might otherwise have been called wide - costing them critical momentum with 32 needed from 15 balls.
It came down to Somerset needing 29 from the last two, a task that ultimately proved too much. Douthwaite picked up a wicket when Green heaved in the air to square leg and Vaughan's boundary off the last ball was academic.
