Sir Alastair Cook struck his 74th first-class century as Essex took advantage of perfect batting conditions in their LV= Insurance County Championship clash with Somerset.
Former England captain Cook converted to three figures in 210 balls before reaching 128 as Essex racked up 360 for four on the opening day with Matt Critchley adding a sublime 119.
A stand of 115 between makeshift opening partnership Phil Salt and George Balderson saw Lancashire take charge against Hampshire at Southport.
Having dismissed the visitors for just 142, helped by three wickets apiece for Tom Bailey and Will Williams, Salt and Balderson made light work of Hampshire’s much-vaunted bowling attack as they powered their way to 139 for one at the close, trailing by three runs.
A stellar century by Jordan Cox rescued Kent as they faced champions Surrey at Canterbury.
The hosts recovered from 41 for five to 301 all out after losing five top-order wickets for seven runs in the space of 31 balls.
Cox led the fightback with 133, exactly 100 of which came after he was dropped by Ben Foakes.
Surrey’s Sean Abbott took four for 52, but the visitors were 18 for two at stumps, trailing by 283 after Agar claimed two late wickets.
Sam Hain’s third century of the season helped Warwickshire get off to a strong start against Nottinghamshire at Trent Bridge.
The visitors ended day one on 361 for five after Hain shared a fourth-wicket partnership of 171 with Dan Mousley (87), opener Alex Davies having earlier scored 93.
In Division Two, Matthew Fisher delivered a timely demonstration of his international potential on a day of Yorkshire domination against Derbyshire at Chesterfield.
Fisher – who played a Test Match in the Caribbean 15 months ago and could come into Ashes reckoning if England’s fast bowlers sustain injuries – returned career-best figures of five for 30 to skittle Derbyshire for 111.
Yorkshire skipper Shan Masood heaped further misery on his former county with 67 – his highest score of the season – and Dawid Malan made an unbeaten 76 before rain ended play early with the visitors 272 for five, 161 ahead.
Only 36 overs were possible between Gloucestershire and Leicestershire at Bristol because of heavily overcast skies and rain.
By the close of a frustrating day, Gloucestershire had posted 108 for three, Ollie Price unbeaten on 26.
Kiran Carlson scored a brilliant century to allow Glamorgan to post 390 with the bat against Durham at Seat Unique Riverside.
Carlson was dropped on 67 and 107, and he duly made the hosts pay with his knock of 162 supported by 60 from Sam Northeast and a quickfire 45 from Billy Root.
Tailenders Jack Carson and Henry Shipley helped Sussex mount a respectable score after an early stumble against Worcestershire.
Sussex recovered from 142 for six to reach 338 for nine at stumps thanks to some late-order hitting from Nathan McAndrew, Carson and debutant Shipley, the latter two putting on 85 for the ninth wicket.
Worcestershire’s Joe Leach finished the day with figures of six for 73.