Nottinghamshire won a thriller against Surrey at The Oval to take control of the Rothesay County Championship race.
Defending champions Surrey, chasing 315 to win, were bowled out for 294 to slip to a first home defeat of the season.
Josh Tongue took the final three wickets including last man Tom Lawes, who made 33 before holing out to Ben Slater on the boundary, to finish with five for 100.
Nottinghamshire, who were deducted one point for a slow over rate, are 14 points clear at the top ahead of their final match against Warwickshire at Trent Bridge, while Surrey visit Hampshire.
Somerset’s title hopes came to an end after they came up short in a draw with Hampshire.
Archie Vaughan took six for 96 but Hampshire, who had been forced to follow on, held out to finish on 201 for eight.
In Division Two, Leicestershire were crowned champions after play against Kent was abandoned on day four without a ball being bowled.
They are now out of reach of second-placed Glamorgan, who were also consigned to a rain-affected draw against Derbyshire.
Glamorgan were still able to celebrate promotion after Middlesex could not force a win against Lancashire.
Lancashire declared on 375 for five with Josh Bohannon hitting 87 off 69 balls and passing 6,000 career runs in the process.
Middlesex were still 65 short of making them bat again on 92 for four when play ended.
Gloucestershire successfully chased down 158 to beat Northamptonshire, losing just three wickets with Ollie Price top-scoring with 54.
Back in Division One, Jonny Bairstow was unbeaten on 64 with Yorkshire 53 runs ahead of Sussex when bad light ensured a draw at Hove.
The visitors lost their first three wickets for six runs but recovered to reach 109 for three in their second innings.
Durham’s Emilio Gay scored 161 and Will Rhodes finished unbeaten on 151 as their match with Worcestershire, whose relegation was confirmed on day three, ended in a draw.
Durham had reached 450 for six – securing a maximum five batting points ahead of a potential relegation shoot-out against Yorkshire next week – in reply to 591 for nine declared when the teams shook hands.
Day four went the same as days one and three at rain-hit Edgbaston where Essex drew with Warwickshire.