Glamorgan recorded a Vitality Blast double over holders Somerset with a thrilling four-wicket win thanks to a boundary off the last ball at the Cooper Associates Ground, Taunton.

The hosts posted 202-6 after losing the toss, skipper Lewis Gregory top-scoring with 54 off 28 balls, sharing a fifth-wicket stand of 90 with Tom Abell (41). Dan Douthwaite was the most successful Glamorgan bowler with 2-35 from four overs.

In reply, the Welsh county managed 203 for six off 20 overs, Sean Dickson hitting 63 from 36 deliveries and Asa Tribe contributing 48 before Jimmy Neesham hit the winning four off the final delivery shortly after a third delay because of floodlight problems in the last over.

Somerset openers Tom Banton and Josh Thomas put together a half-century opening stand in under five overs before Banton, who had smacked five fours and two sixes in his 39, was caught at deep square off former team-mate Ned Leonard.

Leonard went on to concede 50 from three overs. But Glamorgan fought back, Thomas caught for 18 off Ben Kellaway with the total on 60 at the end of the powerplay.

Soon it was 83-4 as Jordan Hermann was run out by Kiran Carlson responding to a poor call by Abell and Thomas Rew was bowled by Douthwaite for two.

Abell and Gregory turned the tide, the latter striking four sixes in reaching a 24-ball half-century and the pair taking 24 off the 15th over, sent down by Leonard.

Abell had faced 28 balls when caught at deep square off Douthwaite. Gregory quickly followed, run out by wicketkeeper Will Smale attempting a cheeky single, but Daniel Sams ensured Somerset would pass 200 with 24 off 12 balls.

Carlson hit Craig Overton for six in the first over of Glamorgan’s reply and followed up with another maximum in the second, bowled by Josh Shaw.

Their innings was then interrupted when the floodlights failed. The umpires consulted both captains and play resumed with one light still off.

Carlson, on 29, was dropped by Thomas Rew at mid-wicket off Sams’ first ball of the innings, but perished to the next, skying to long-off. Kellaway quickly departed to Jake Ball and Smale fell for 22, lbw trying to pull a ball from Overton, who ended the powerplay with a wicket maiden to leave Glamorgan 55-3.

Dickson was dropped on 14 by Ball at third-man off Gregory. It looked like proving an expensive miss as the former Somerset man cleared the ropes off first Shaw and then Lewis Goldsworthy before another six off Sams brought up a 33-ball fifty.

Sams responded with a slower ball that saw Dickson offer a high return catch to make it 144-4 after 15 overs. Tribe was going well on 26 and he accelerated by taking two fours and a six off Ball before being caught at short fine leg off a Shaw full toss.

Glamorgan needed 16 off the last over, bowled by Ball. Douthwaite hit the second ball for six, but after the lights went out again he was caught at long-on, giving Neesham the chance to hit the winning boundary through the leg side with the last ball of the contest.