Hampshire 221 for 3 (Donald 57, Markram 61, Northeast 51*) beat Somerset 216 (Bartlett 40, Abbott 3-36) by seven wickets

Hampshire trounced Somerset by seven wickets with 18.3 overs to spare at Taunton to confirm themselves as South Group winners and a place in the semi-finals.

The absence of James Vince and Aiden Markram to international duties could weaken them in the knockout stages, but Hampshire might just have found an answer in the form of Aneurin Donald. Given his head as an explosive player at the top of the order while Vince was already donning an England shirt in Dublin and Cardiff, Donald has worked out rather well.

He followed up his 41 against Sussex at the Ageas Bowl on Thursday with 57 from 53 balls in front of an excellent crowd at Taunton. That Somerset had little chance of defending their 216 on a used but reliable surface became apparent as early as the fifth over when he took successive sixes off Josh Davey, the second of them a wristy affair over midwicket which told of his potential. A third followed late in his innings when he deposited Roelof van der Merwe into the Sir Ian Botham stand before falling later that over by skying to mid off.

Once a youthful carrier of Glamorgan hopes, Donald switched to Hampshire late last season with the aim of furthering his ambition to become the first Wales-born player to represent England since Simon Jones in 2005. He said he thought his game was stagnating, and he got out just in time before somebody write a song about him: you don't have to show much promise in Glamorgan for the rhapsodies to begin.

Those England aspirations remain a long way off as a record of only one half-century in 27 List A appearances indicated, but there is certainly something about him. He believes that he is ideally suited to the role of top-of-the-order dasher and Hampshire might have made a shrewd - if enforced - call by giving him a run. The recent call-up of Sussex's free-spirited opener Phillip Salt into England's T20 squad has provided further proof that reputations in such a role can be made an instant.

"It's nice to be up there having a bit of a hit," he said. "It can be a pretty tough time down at No 7. Hopefully I can fill a hole at the top of the order. It's something I've always wanted to do. I think my game suits it.

"I knew what I was getting myself into when I joined Hampshire. I had come down to Hampshire late last season just to settle in and I was hanging around trying to get a game. I knew the white ball came round earlier this year so I'd be in the frame to get a go early on."

Tom Alsop also made punishing inroads into Somerset's inadequate total, hitting seamer Davey for 4,4,6,4 before pulling a catch to short fine-leg off Craig Overton to give Somerset a breakthrough. But composed half-centuries from Markram and Sam Northeast followed, Northeast reaching the landmark with the winning blow - a regal one-legged flat bat off the long-suffering Davey to win the game in style.

A May Bank Holiday chill had descended upon the Quantocks and spectators slumped ever deeper into winter coats as seven of Somerset's top eight reached double figures without managing a single half-century.

Yellow is back in vogue here after the local elections - but regretfully for local tastes it was Hampshire who were wearing it. About the best that can be said for Somerset's innings, as they were bowled out with nearly 10 overs unused, was that Kewstoke Village Hall would be £25 better off. Peter Trego had promised £1 a run to their village hall fund-raising, but the new football goal posts will have to wait a little longer after he was bowled by Liam Dawson, trying to cut.

Azhar Ali's cautious innings ended when he was caught at the wicket, trying to run Gareth Berg. There were two top-order wickets, too, for Mason Crane's leg spin, although the first of them, a loopy thigh-high full toss, left him covering his eyes in mild embarrassment as James Hildreth scooped it into the leg side. Tom Abell's full-blooded sweep was more convincing but he picked out deep square.

George Bartlett top-scored with 40 from No. 6, his best List A score, but his inexperience showed in an increasingly skittish innings which saw him perish to an inside-out drive against Dawson. There was even a one-ball partnership between the Overton twins which ended in a first-ball run-out for Jamie. Craig was entirely innocent, responding to his brother's call instantly only for Jamie, somewhat lumbering, to fail to beat Northeast's direct hit from mid-off.

Somerset must now win their final match, under floodlights against Surrey on the same Taunton ground on Tuesday, and hope that they can secure a place in the top three for a play-off berth. Surrey might be bottom of South Group, but they still possess obvious danger for all that. Somerset's head coach Jason Kerr termed their display "disappointing, bordering on embarrassing" as a campaign that began well with four wins but which has now lost further impetus with a third successive defeat.

To satisfy local sentiments they would have to thrust the England left-arm spinner Jack Leach into the side, but he has little experience of white ball cricket and that is highly unlikely. If they balance up their side, then offspinning all-rounder Dom Bess, who started the tournament, is a likelier choice. Davey, or Jamie Overton, who came unscathed through his first bowl of the season after returning from his latest injury, would be expected to make way.