Somerset kept alive their hopes of a maiden LV County Championship title with a 219-run win over relegation-threatened Essex at Colchester.
Essex resumed on the third morning at 38-1 in pursuit of a victory target of 432.
Opening batsman Billy Godleman produced a defiant half-century but there was little support lower down the order and the home side were eventually all out for 212 just before tea.
Seam bowler Peter Trego removed dangerman Ravi Bopara (15) and Godleman (53) during the morning session as Essex slipped to 127-5 at lunch.
Trego, who finished with figures of 3-27 from 11 overs, added the scalp of Mark Pettini (6) early in the second session before his fellow medium pacer Zander de Bruyn took centre stage.
The South African bagged 4-23, including the final three wickets in the space of eight balls to condemn Essex to their fifth defeat of the season.
Somerset's 20-point haul moves them above Yorkshire and into second in the table, four points behind leaders Nottinghamshire, who have a game in hand.
Essex, meanwhile, had their misery increased by a two-point deduction for a slow over-rate during the match and remain second bottom, having played at least a game more than all of their relegation rivals.
Marcus Trescothick hit the third double century of his career on Thursday as title-chasing Somerset assumed a commanding position in their match against Essex at Colchester.
Trescothick's innings of 228 not out was the highest score by a Somerset player against Essex and carried the visitors to 367 for eight declared in their second innings.
Playing a series of magnificent drives, the former England star smashed seven sixes and 23 boundaries in his 230-ball innings - more than making up for his third-ball duck on the opening day.
He was put down twice - on 85 at slip by Mark Pettini off Matt Walker and again on 178 by Chris Wright on the square leg boundary - but made 157 for the fourth wicket with James Hildreth (59) and 127 for the ninth wicket with Murali Kartik (52).
David Masters was the only Essex bowler to command any real respect, picking up three for 53 in 18 overs - Danish Kaneria picking up Hildreth's wicket albeit at a cost of 120 in 20 overs.
Relegation-threatened Essex, who had earlier lost their four remaining first innings wickets to finish 151 all out, were therefore set a monumental victory target of 432 and in the 10 overs left they fell to 38 for the loss of Jaik Mickleburgh.
A total of 16 wickets fell on the first day of a fascinating LV= County Championship Division One clash between Essex and Somerset at Colchester.
Having dismissed Somerset for 215 in their first innings, Essex then slumped to 126-6 in reply to leave the match finely poised heading into day two.
Ravi Bopara spurned a golden opportunity to press his claims for inclusion in England's Ashes party as he made just one in front of national selector Geoff Miller.
Bopara was trapped leg before by Charl Willoughby as Essex lost early wickets with his wicket being sandwiched between two for Ben Phillips who dismissed both Jaik Mickleburgh and Matt Walker cheaply.
Alfonso Thomas then came back to claim the wickets of Billy Godleman (32) and Mark Pettini (34) and when James Foster (16) became Willoghby's second victim late on Somerset ensured they were right back in the contest.
Earlier in the day they had disappointed with the bat with the exception of James Hildreth who continued his excellent season.
Plenty of Somerset batsmen got starts, but few could provide Hildreth with sustained support as David Masters ripped through their line-up to finish with figures of 5-43 from 21.1 overs.
Hildreth made 84 from 138 balls and shared in half-centru stands with Zander de Bruyn (34) and Peter Trego (27) to ensure the visitors got up to and beyond the 200-mark.