Opener Tom Lammonby returned to form to revive Somerset’s Rothesay County Championship title challenge with his highest score of the season on an absorbing second day against Sussex at Hove.

The left-hander has had a lean summer and averaged 28 coming into this match, but a chanceless 74 off 143 balls – with power to add tomorrow – helped Somerset reach 167 for 2 at stumps, a lead of 119.

They had trailed by 48 on first innings after a last-wicket stand of 40 by John Simpson and Jaydev Unadkat swelled Sussex’s total to 250 before Lammonby and Josh Thomas took advantage of improving batting conditions with 92 for the first wicket.

Sussex skipper Tom Haines rotated his three quicks but there was little sign of a breakthrough until the 23rd over when left-armer Sean Hunt switched to the sea end and Thomas fenced at a ball that bounced more than he expected and the diving Charlie Tear took a fine low catch at slip.

Archie Vaughan was caught behind off the inside edge driving at Unadkat after he added 49 with Lammonby, but Henry Nicholls and Lammonby negotiated the remaining ten overs to stumps.

Sussex still harbour outside title hopes themselves but will feel this was an opportunity missed. At 149 for 2 with Tom Clark scoring at a run-a-ball they would have fancied establishing a much bigger advantage than they got.

But the left-hander’s dismissal for 85 (83 balls, 15 fours, 1 six) precipitated a collapse that saw seven wickets fall for 61 in 29 overs.

Clark wafted a length ball from Craig Overton to slip without moving his feet, and he wasn’t the only Sussex batter complicit in his own downfall.

James Coles got a thick inside edge onto his stumps when he tried to swat a delivery from Gregory into the leg side but Somerset’s seamers deserve credit for bowling a touch fuller.

Overton finished with 4 for 66 and, as well as Clark, he also removed Tear after the pair added 92 for the third wicket. Tear played well for his 34, but two overs after dismissing Clark Overton got one to swing in and straighten.

Overton returned after lunch to pick up Jack Carson and Henry Crocombe in the space of three deliveries while debutant Joey Evison hit a solitary boundary in a curious innings spanning 18 deliveries before driving away from his body at Lewis Gregory.

It wasn’t all plain sailing for Overton. In the slips he dropped Tear on 10 and Simpson on 14 and the second spill could yet prove important.

When Hunt was ninth out Sussex still trailed by one but Simpson used all his experience to protect Unadkat while flaying anything loose through gaps in a well-populated boundary. He was put down for a third time on 56 by Migael Pretorius at mid-off.

Unadkat joined in the fun – his two scoring shots were both leg-side sixes – while Simpson’s unbeaten 64 was his highest score in eight Championship innings. Sussex also claimed a precious batting bonus point, which might prove important at the end of the season.

It needed Jack Leach to end the fun when Unadkat missed a sweep. Leach could have a bigger role to play when Sussex start their run chase, but a poor forecast on day three may scupper both teams’ chances of forcing victory.