Somerset 181 for 5 (Conway 70*, Walker 3-15) beat Glamorgan 107 (Goldsworthy 3-14, van der Merwe 3-10) by 74 runs
Somerset sealed a place in the Vitality Blast quarter-finals as they hammered Glamorgan by 74 runs at Sophia Gardens.
New Zealand run machine Devon Conway batted Somerset's full 20 overs for an unbeaten 70 from 52 balls as Glamorgan's bowlers struggled at both ends of the innings.
In between, Roman Walker impressed with 3 for 15 from his four overs but Glamorgan's batsman were nowhere near as good as they were bowled out for just 107 with First Minister of Wales Mark Drakeford watching on.
Somerset - who were without England pair Lewis Gregory and Tom Banton - won the toss and unsurprisingly chose to bat on a stunning evening in the Welsh capital.
Conway struck two leg-side boundaries from Andrew Salter's first over, but Glamorgan's poor bowling gave their opponents a flying start. Dan Douthwaite's first over went for 16 and included a ball which went for five wides. Two more wides and a six struck by Steve Davies followed.
Timm van der Gugten dismissed Davies, caught behind by Chris Cooke for 22, but it was a rare good delivery as Glamorgan strayed on to leg stump far too frequently.
Somerset were 55 for 1 after six overs and 84 for 2 at the halfway stage, but Walker dragged Glamorgan back into it with the wickets of Will Smeed and veteran James Hildreth.
Lewis Goldsworthy smashed Marnus Labuschagne for six down the ground, but Walker showed him how it should be done with his third wicket of a superb spell.
Conway watched the wickets fall at the other end until Tom Lammonby joined him and smashed Van der Gugten for four, four and six from the first three balls of the 17th over.
Conway went past 50 and then joined in the fun by hitting the struggling Douthwaite for six although the Glamorgan seamer did dismiss Lammonby for 34 thanks to a smart Salter catch.
Kiran Carlson smashed Jack Leach for six on the second ball of Glamorgan's response but was caught and bowled by the England spinner on the fourth. Colin Ingram carted a six over midwicket but he too went caught and bowled, this time at the hands of Craig Overton for 19.
Glamorgan were 36 for 2 after the first powerplay. David Lloyd hit Goldsworthy's first ball to Overton at cover and it left Labuschagne and Billy Root needing 122 from the final 10 overs. Glamorgan didn't get close. Labuschagne pulled Marchant de Lange to the mid-wicket boundary where Roelof van der Merwe took a stunning catch and from there the Welsh side folded. Somerset's spinners were far too good with Goldsworthy finishing with 3 for 14 and Van der Merwe 3 for 20.