Somerset 372 (Trescothick 116, Petersen 76, Jordan 5-76) beat Sussex 142 (Wells 79*, Gregory 5-49) and 219 (Joyce 93, Gregory 4-48) by an innings and 11 runs
Scorecard
Somerset needed just 75 minutes of the final day to record their first win of the season by an innings and 11 runs against the leaders Sussex.
Starting the day 68 runs short of making their visitors bat again, Sussex saw their hopes of taking the game into any sort of a contest ended when Ed Joyce chopped on for 93.
Joyce represented Sussex's best chance of salvation and, after he fell just short of a third century of the season, Somerset quickly wrapped up the tail and Sussex's innings for 219.
They started as they went on with an early wicket as England hopeful Chris Jordan, a useful lower-order batsman Sussex will have hoped could stick around, edging Jamie Overton to James Hildreth at first slip for 7.
James Anyon joined Joyce in the middle and the pair at least looked like sending Somerset out again before Joyce perished. Marcus Trescothick's decision to make a bowling change 45 minutes in paid off with Lewis Gregory, the game's stand-out bowler, coming on and removing Joyce, who tried a nudge to third man but ended up diverting the ball onto his stumps.
That was the main breakthrough Somerset had sought, before another bowling change produced dividends in the next over. Peter Trego was handed the ball by his skipper and he needed five balls to snare Anyon, who dragged a short delivery from the all-rounder down the throat of Chris Jones at midwicket for 10.
The game was pretty much up at that point, and it was for sure when Jon Lewis lost his middle stump to Gregory for seven, giving the bowler impressive match figures of 9 for 97.