Sussex will aim for a seventh victory of the season.

Score Update: Sussex 407 for 5 (Simpson 112, Hughes 83, Clark 73, Crocombe 54) leads Glamorgan 186 (Carlson 56, Unadkat 4-52) by 221 runs.

Captain John Simpson became the first Sussex player in a decade to achieve five Vitality County Championship centuries in a single season, as the second-division leaders asserted their dominance over Glamorgan at Hove. With an impressive unbeaten 112, Simpson also crossed the 1,000-run milestone as Sussex responded to Glamorgan's subpar total of 186 by reaching 407 for 5, establishing a commanding 221-run lead.

With promotion contenders Yorkshire and Middlesex poised for victories in their matches, securing a win for Sussex is vital. After a shaky spell just before lunch, where they lost four wickets for 25 runs, the team quickly regained control at the 1st Central County Ground.

Simpson has shared a significant partnership of 194 for the fifth wicket with Tom Clark, who remained not out on 73. Just before the players were taken off due to bad light at 4:20 PM, the duo scored 19 runs off ten balls, ensuring Sussex achieved their fourth batting point.

Ed Joyce was the last Sussex player to match Simpson's prolific form during his tenure, and Simpson has consistently ensured that his team capitalizes on advantageous positions throughout the season.

As the day began, Daniel Hughes and nightwatchman Henry Crocombe extended their second-wicket partnership to 78, with their only scare occurring when Dan Douthwaite dropped a challenging catch at midwicket while Crocombe was on 25. While Hughes appeared set for consecutive centuries, he fell short at 83, hitting 14 boundaries before offering a simple catch to midwicket off Douthwaite, Glamorgan's standout bowler on a rough day. Crocombe reached his first-class fifty with a powerful shot through the covers before being dismissed at short leg while attacking off-spinner Ben Kellaway.

Kellaway, who showcased his ambidexterity by briefly bowling left-arm spin later in the day, managed to dismiss Tom Alsop caught at slip and saw James Coles, the only right-handed batsman in Sussex's top order, edge a catch he could have avoided in the final over before lunch, giving Douthwaite his second wicket.

Clark achieved only his third fifty of a challenging season, but initially struggled against Kellaway. He didn’t register a boundary until his 58th delivery, cutting Kellaway through backward point. However, as Simpson began to counter-attack, Clark gained confidence, helping Sussex take control.

Glamorgan bowled just eight overs of seam with the new ball before Kellaway returned to the attack, impressing with his control on the spinning surface in just his fourth first-class match. As the sixth-wicket partnership flourished, the focus shifted to how many batting bonus points Sussex could amass in the 110 overs allocated.

Simpson hit two boundaries off Kellaway, the second bringing his total to 15 first-class centuries. In a thrilling over, ten runs came off the penultimate over, while a six off Ned Leonard's first delivery of the next over secured Sussex’s fourth batting point with two balls remaining.

As light conditions deteriorated, umpires Nigel Llong and Sue Redfern called the players off the field. With two days remaining and a favourable weather forecast, Sussex will feel confident in their ability to capitalize on their advantage and aim for a seventh victory of the season.