It was a day for veteran runscorers as Marcus Trescothick followed Trott's century by reaching 25,000 first class runs as Somerset replied to Warwickshire’s 413 all out.
The former England opener was unbeaten on 41 at stumps in a total of 94 for four, having begun his innings needing 29 to reach the remarkable milestone. Grant Thornton, on his Championship debut, took two for 14 from five overs.
Earlier, Jonathan Trott had made 175 in Warwickshire first innings, the 20th time he had gone past 150 in the first class cricket. He received good support from Sam Hain (39), Tim Ambrose (63) and Rikki Clarke (57), while there were three wickets each for Jamie Overtoon and Roelof van der Merwe.
Play began on time, with Warwickshire 124 for three and Trott unbeaten on 50. The first half hour saw him survive a confident appeal for a catch behind down the leg side off Peter Trego, who then dropped him at fourth slip off Craig Overton before he had added to his overnight score.
The total had progressed to 150 when Hain was bowled by a full delivery from left-arm spinner Jack Leach. It was Somerset’s only success of the morning session as Ambrose and Trott took the score to 215 for four at lunch.
Trott was 13 short of his hundred and there were no more alarms as he brought it up with three successive boundaries off the previously economical Leach. He had faced 212 balls and hit 16 fours.
Ambrose played confidently to reach a 100-ball half-century, with 5 fours and a six, before falling to an unusual and brilliant catch by Trescothick, who anticipated a sweep off Leach and moved from slip as the shot was being played to take a left-handed catch at leg slip.
Rikki Clarke came in with licence to attack as Warwickshire chased maximum batting points and was soon on the attack. Trott moved comfortably to 150 and the pair had added 95 in 16.2 overs when he was caught at backward point off Jamie Overton, having batted for six hours and extended his boundary count to 22 fours and 3 sixes.
Tea was taken on Trott’s dismissal with Warwickshire 391 for six, needing nine runs off as many balls for a fifth batting point.
They fell short as Keith Barker was caught at mid-wicket and Clarke failed to make contact with two big swings at the end of the 110th over, bowled by van der Merwe. A clatter of wickets followed, the last five falling for 22 runs.
Somerset had progressed to 21 in reply when Dean Elgar was trapped in front during an impressive opening spell from Barker. Tom Abell’s wretched run continued when on eight he jammed down on a full ball from Jeetan Patel and watched in horror as the ball trickled back onto his stumps.
After Trescothick had acknowledged the applause of the crowd, having moved onto 31 and had his latest achievement announced over the tannoy, Warwickshire struck two more blows.
James Hildreth, on 14, was pinned lbw on the back foot by Thornton for the seamer’s maiden Championship wicket. And the 24-year-old quickly followed up by having the out-of-form Steve Davies caught at short-leg for seven.
Of his achievement in passing 25,000 first class runs, Marcus Trescothick said: "One of the office staff told me around ten days ago how close I was to 25,000 and I have been sweating on it since then.
"I knew when I went in that I was 29 away and it got a bit tense as I moved closer. It is an achievement I am proud of and I'll probably reflect on it for a while when I am home with my family tonight.
"There is still a big job for me to do in this game. It wasn't a great day for us and we need to concentrate hard tomorrow to make sure we come away with a draw."