Somerset 201 for 3 (Thomas 136*) lead Yorkshire 162 (Gregory 6-43) by 39 runs

After losing the toss, Yorkshire progressed to 124 for 3 under overcast skies, with Joe Root and Jonny Bairstow going well, only to lose their last seven wickets for 38 runs, Gregory taking five of them in completing 16 probing overs for figures of 6 for 43.

Root made 33 and Bairstow 34, while opener Fin Bean contributed 35 to a total of 162. In reply, Somerset slipped to 35 for 3 before 21-year-old Thomas led an impressive recovery with 136 not out off 150 balls that saw them close on 201 for 3, Tom Abell unbeaten on 41.

A green-tinged pitch offered pace and movement for the seamers. Yorkshire had already lost Adam Lyth, lbw to left-arm seamer Alfie Ogborne, when the floodlights were switched on at 11.20pm.

James Wharton spent 19 balls on nought before edging Gregory to wicketkeeper James Rew, the delivery after being dropped at second slip by Overton, to make it 48 for 2. That became 64 for 3 when Bean nicked another catch to Rew in Migael Pretorius’ second over.

Root and Bairstow demonstrated their quality with a half-century stand off just 42 balls, Root blossoming from a cautious start with three straight-driven fours in an Ogborne over. Bairstow was aggressive from the outset, but had a life on 22 when the normally reliable Overton spilled another slip chance, this time off Pretorius in the final over before lunch, which was taken at 114 for 3.

With ten runs added in the afternoon session, Gregory pierced Root’s defence and bowled him off an inside edge. It was 140 for 5 when Overton responded to dropping Bairstow by taking his wicket, courtesy of an inside edge through to Rew.

Gregory then struck three times in the 37th over, bowling Matthew Revis, shouldering arms, with the first ball before pinning former Somerset team-mate Dom Bess leg before with the fourth and then having Logan van Beek caught at third slip off the sixth.

The inspired Somerset captain had George Hill dropped on 1 by Abell at first slip before clean bowling Jhye Richardson aiming an airy drive. Overton finished the Yorkshire innings by having Hill caught for 18 off a top-edged pull.

Somerset’s reply began badly when Archie Vaughan fell for 7, caught behind edging a defensive shot off Jack White and Tom Lammonby followed for 5, trapped lbw by some late inswing from Richardson. When James Rew was well caught low down by Bean at third slip off White for 7, the hosts were in trouble. But Thomas counter-attacked with an array of sweetly-timed shots just before tea, which was taken at 63 for 3.

The left-hander continued to flourish after the break, reaching his half-century off 54 balls, with nine fours. On 10, he had edged Richardson between wicketkeeper Bairstow and first slip at catchable height and it proved a big moment.

A pulled six off Matthew Revis took Thomas past his previous best Championship score of 86, made against Essex at Chelmsford last season. Another pulled boundary off the same bowler brought up a memorable hundred, off just 109 balls, with 14 fours.

Abell was a reassuring presence at the other end as the pair put together a century partnership off 149 deliveries. He too cut loose with six over long-on off Bess to take Somerset into the lead. By stumps the stand was worth 166.