Alex Davies hit a maiden double century as Warwickshire piled on the runs on the opening day of their Vitality County Championship encounter with Durham at Edgbaston.
Fellow opener Rob Yates also cracked 191 in an extraordinary first-wicket partnership of 343 with outstanding skipper Davies, whose unbeaten 226 came from 274 balls with 25 fours and three sixes.
To compound the misery for promoted Durham, who had won the toss, Will Rhodes reached 60 not out to take the hosts past maximum batting points and to 490 for one before the close.
Champions Surrey took command against Somerset at The Oval despite a century from Tom Lammonby.
Lammonby (100) and Matt Renshaw (87) got Somerset off to a fine start by putting on 178 for the second wicket but the loss of seven wickets for 20 runs undermined their efforts.
Captain Lewis Gregory (50) lifted the score to 285 but Cameron Steel (four for 50) wrapped up the innings before Surrey openers Rory Burns and Dom Sibley chiselled 42 off the lead without loss.
Joe Clarke continued his excellent start to the season with another century as Nottinghamshire closed on 305 for six against Worcestershire at Trent Bridge.
Following up his ton against Essex last week, Clarke hit 105 and shared in a third-wicket stand of 133 with Ben Slater (70) as the hosts recovered from the loss of two early wickets.
Dean Elgar (120) scored his first Essex century and Matt Critchley (103no) also reached three figures against Kent at Chelmsford.
Jordan Cox added 67 and Michael Pepper 49 as the hosts amassed 421 for six at stumps.
Hampshire were 305 for six at the end of day one against Lancashire at the Utilita Bowl.
Liam Dawson was unbeaten on 61 after solid efforts from Tom Prest (85), James Vince (56) and Nick Gubbins (50).
Australia’s Nathan Lyon (two for 97) bowled 32 overs as Lancashire kept themselves in the game.
In Division Two, spinner Alex Thomson took a career-best seven for 65 as Derbyshire bowled out Glamorgan for 287 in Cardiff. Kiran Carlson was the hosts’ top-scorer with 74.
Derbyshire were 46 for one in response.
Emilio Gay’s unbeaten 165 helped Northamptonshire to 311 for three against Middlesex at Wantage Road. Captain Luke Procter added 73 in a second-wicket partnership of 189.
Pakistan captain Shan Masood’s 140 was the mainstay of Yorkshire’s 326 against Gloucestershire at Bristol. Jonathan Tattersall (58) and Matt Milnes (51) also contributed but Zaman Akhter’s five for 89 helped the hosts hit back before they ended the day on 28 for two.
Liam Trevaskis was 82 not out as Leicestershire closed on 326 for eight against Sussex at Grace Road. Rishi Patel (87) and Peter Handscomb (51) also hit half-centuries.