Resuming on 337-9 after losing late wickets on day one, Somerset earned a third batting bonus point for the first time in the season, reaching 354 to the delight of an appreciative away support.

Last man Jake Ball cover-drove two fours and deflected a leg-side ball to the boundary with his pads, before being bowled by Mason Crane’s googly.

Glamorgan’s innings got off to a frantic start as Zain Ul Hassan took two boundaries off a Lewis Gregory over that also included two no balls.

Then Asa Tribe slashed Jake Ball’s first delivery over the slips and prodded the second to fourth clip, leaving the score 16-1 after eight balls.

Ul Hassan edged Gregory to slip for 16 before Pretorius took over with a hostile spell, having Kiran Carlson caught at slip for 21, trapping Colin Ingram lbw first ball and re-arranging the stumps of former team-mate Sean Dickson.

From 93-5, Kellaway and Chris Cooke launched a strong fight-back with a stand of 80, both men driving strongly down the ground while Cooke pulled a big six off Gregory.

Kellaway had eight fours on the board when England left-arm spinner Jack Leach was eventually brought on to vary the diet of seam and struck in his second over, Kellaway chopping onto his stumps,

With Chris Cooke falling leg-before to Craig Overton for 39, Glamorgan were back in trouble and that worsened when Mason Crane was questionably given out caught behind down leg-side off Ball, with the ball appearing to strike Crane’s thigh-pad.

Norton (11) stayed with Timm van der Gugten long enough to avoid the possibility of the follow-on before chipping Gregory to mid-on

Meanwhile van der Gugten was last out for 30, caught behind hooking at Overton after a listless passage of play.

Van der Gugten was off the field after taking a blow to the elbow when Somerset went into bat again, allowing Norton to steal the spotlight.

He struck Rew on the glove with the ball lobbing to Tribe at slip, then found the edge of Lammonby’s bat with another fine delivery and drilled the hat-trick delivery into Vaughan’s pads, with umpire Paul Pollard’s upraised finger seeing Norton engulfed by his team-mates.

England paceman Jeff Jones was the previous youngest to achieve the feat for Glamorgan aged 20, back in 1962.

Josh Thomas fell to Ryan Hadley for 15, caught hooking off a top edge, to leave the Somerset innings in disarray.

That deepened when night-watchman Jack Leach edged Hadley to slip, and Norton had Will Smeed caught behind in the final over for the fifth duck on the Somerset card.

Their first innings advantage leaves the visitors still with a significant lead in the game on a largely bowler friendly pitch, but Norton’s exploits will be long remembered at Glamorgan as statisticians were left hunting through the record books.

Glamorgan’s Tom Norton told BBC Sport Wales:

“I remember the balls, I don’t remember much of the (on-pitch) celebrations after. I saw the nicks and the lbw, and just ran off wildly.

“I’d said to myself it would be good if we could get two wickets tonight, so it’s really good to have them six down. With Timm not being there, Zain and Hadders (Hadley) bowled exceptionally as well, we all came together and bowled brilliantly.

“Coming back out and taking four is stuff I’d never even dreamed about! It’s really special to have my name in the history books.

“But we need to get back out there, take the (remaining) four wickets and get at them with the bat.”

Somerset bowling coach Steve Kirby said:

“A lot of credit has to go to our bowling group to bowl them out for 229, it’s a new ball pitch and it does change when it gets a bit older.

“So I’m glad what’s happened has happened when we’re 150 ahead rather than 150 behind!

“It was an incredible spell of bowling from Norton, I’ve been really impressed with him since the first innings. There were some poor shots but we’ve got a lot to come and a massive opportunity to win this game.”