Sussex made a brilliant start with home openers Archie Vauan and Lemonbi against the Samarset, which fell for the left -handed scene hunt for ducks.
Henry Crockombay had 82–5 after the removal of Rev brothers, James and Thomas for 29 and 30 respectively, but Thomas scored 50 off 58 balls, as he and Hill added 59 for the sixth wicket.
Thomas was caught behind Hunt (3-35), but Hill (55) brought its second gradual 50, it was one of 62 balls, and placed at 67 with Kian Roberts (29) at 67, before Somerset was excluded from the midway via the 48th over.
Tom Hans left for Sussex early, but they reached 60, before Lamonbi had caught Charlie in the cover and won the LBW decisions against Fen Hudson-Prantis and John Simpson, which were in the same over with involvement delivery.
Tom Clarke (34) chased the next, caught from a leading edge to mid-on, and although Jack Carson weighed with 35 balls in 34 balls, wickets continued as Sussex slipped for his third defeat.
“After getting out of the third ball for a duck, I was not really expecting a lot from the day. But I got an opportunity to get some overs with a new-Ish ball. It turned around the early doors, helping me to help,” Lemonbi said.
“I got lucky with the first one and then I got my rhythm more a little more. I was very happy to take for my first five. It’s a very good and very special moment.”
The victory lifted Somerset to second place above Middlesex, the leaders’ Yorkshire’s points, while Sussex sixth, two with four points behind the top three.
