Somerset 282 (Abell 82; Singh 5-72) and 265 for 4 dec (Trescothick 119*, Hildreth 68, Abell 51) lead Warwickshire 146 (Barker 52; Leach 5-50, Overton 4-33) and 172-6 (Trott 74) by 229 runs.
Marcus Trescothick is literally part of the furniture at Taunton, where they named a stand after him. If there is a ground he can call a home from home, though, then surely it is this one. In 19 first-class matches at Edgbaston he has six hundreds, 1,596 runs in total and averages 53.20. Nowhere else outside his home county has he been so successful.
The latest of those has probably sounded the death knell for Warwickshire's membership of Division One of the County Championship. Six wickets down going into the final day, in pursuit of a nominal target of 402, it will need an act of supreme generosity on the part of the weather if they are to avoid a seventh defeat of the season.
Trescothick, who numbered 15 fours in his unbeaten 119, shared partnerships of 148 with James Hildreth, building on 52 overnight, and exactly 100 with his young successor as captain, Tom Abell, who those two apart batted as well as anyone faced with the difficulties posed by this pitch, making half-centuries in both innings.
The frustration this brought to Jeetan Patel, who bowled 24 wicketless and at times luckless overs, can only have been matched on the day by Ian Bell, whose troubles continued. For the second time in the contest he was dismissed by Jack Leach, the Somerset left-arm spinner, who did for him with prodigious turn in the first innings and this time foxed him with an arm ball, bowling him through the gate.
If Bell cast the odd envious glance in Trescothick's direction, fielding in the corner of his eyeline at wide second slip, it would have been understandable. His former England team-mate is 42 in December, more than six years his senior, yet it is Bell with whom time seems to be catching up. He does not have a century since April last year and has passed fifty only three times in 19 attempts in 2017.
His latest trough - which now extends to only 94 runs accumulated in his last eight innings - has prompted him to resign the captaincy in order to focus on his batting yet there has been no benefit so far. The three-year contract he signed in April this year is beginning to look a little optimistic.
Still, he may recall that there were dark mutterings about Trescothick having perhaps outstayed his welcome in 2013, when he failed to make a hundred. He soon put that right.
Indeed, he has made 14 since, this one his 51st for Somerset in first-class cricket and his 65th in all. He is a phenomenon, his natural gift of hand-eye co-ordination, always his game's strength, showing no sign yet of any serious decline. Trescothick is signed up for another year after this one and there is no suggestion that it will be his last.
Sixty-five hundreds or not, this one will be remembered. "That was a special century for me because it has been a tough season so it's good to come through and get the runs I've been looking for for a long period of time," he said. "It's not been the luckiest of seasons for me but also I have not played very well at times.
"Edgbaston is a place I have always enjoyed playing. Back when I was playing for England it was always a good place to bat. It's a nice ground and the atmosphere is always good and the pitch is always good.
"This has been a good cricket wicket with a bit in it for all involved, a bit of swing on the first day and some spin, then it got easier to bat on on the second day, though it still spun a bit. It has got a bit more inconsistent but you can still dig in and get runs.
Whether he will be taking on Division One bowlers in 2018 remains to be seen. If a win for Somerset here would all but seal the fate of their opponents, it will not banish their own uncertainties. There is still a gap to close above them and it is still possible - freakishly - that their final match against Middlesex, who pipped them for the title last year, could be for the second relegation place.
Compared with the mayhem of day two, when 18 wickets fell, day three was much quieter, the pitch seeming to lose some of its menace. It did not help Warwickshire's cause that Keith Barker, who had batted in some pain on Wednesday, was not able to bowl because of a back problem.
With limited options and no sign of a breakthrough as Somerset briskly added to their 211-run overnight lead, Jonathan Trott turned - out of inspiration or desperation to Matthew Lamb, his 21-year-old No 5 batsman, to fill in as a fifth bowler.
Lamb had not previously bowled in a first-class match - although this is only his fifth - but his steady medium pace is not even called on by his Birmingham League side with any regularity. It probably surprised everyone, then, possibly himself included, when his second ball had Hildreth reaching outside off stump and nicking to second slip.
It was the only wicket of the morning and with a lead of 354 at lunch Abell might have safely declared there and then. In the event, he not only allowed time for Trescothick to complete his century but for the lead to pass 400, which seemed to be on the cautious side - more so when Warwickshire then lost both openers for 21 as Tim Groenewald struck twice in five balls in his second over.
The former Derbyshire seamer came back to dismiss Lamb in his second spell after Warwickshire had reached tea at 73 for 3. The remainder of an elongated evening session - with time still being added to compensate for the first-day losses - then belonged to Warwickshire until the last 10 minutes, when Dom Bess dismissed both Trott and Barker leg before in the space of three balls.
Trott had made 74, raising hopes - slim ones, granted - of escaping with a draw if the weather were to turn nasty on the final day. The odds are now that they will not.