Keaton Jennings scored an unbeaten double century for Durham while Steve Magoffin picked a five-wicket haul for Sussex as day one of the latest round of County Championship kicked-off on Monday.
Elsewhere, Somerset bowled Yorkshire for 145 and scored 107 for one at stumps to end the day in a dominating position.
Durham won the toss and elected to bat first. After being 105 for one at one stage, Mark Footitt (4-88) and Stuart Meaker (3-104) inflicted heavy damage and restricted the home side to 232 for seven.
However, Jennings (200 not out) kept the fight going at one end as he reached his century off 171 deliveries and needed 112 balls more to complete what was a splendid double century.
His partnerships with Mark Wood (28) and Graham Onions (7 not out) helped Durham reached 393 for nine at stumps on day one.
The top-order of Middlesex delivered the goods after they were forced to bat first by Lancashire. Sam Robson (77) and Nick Gubbins (69) shared a 127-run opening stand to lay the platform.
Even though Middlesex lost both the openers in quick succession, another 97-run stand between Nick Compton (56) and Dawid Malan (49 not out) ensured Middlesex ended steady at 258 for three.
Worcestershire won the toss and elected to bat first but they were troubled early by Steve Magoffin (5-38) and Chris Jordan (2-60) and were reeling at 178 for seven.
Skipper Daryl Mitchell (75) and Ben Cox (69) were the only saving grace for Worcestershire as they managed 306 before they were bowled out.
Miguel Cummins (3-30) had a memorable outing with the ball as they reduced Sussex to 50 for four at stumps on day one, trailing Worcestershire's first innings total by 256 runs.
Yorkshire won the toss and opted to bat but Craig Overton (3-32) and Jim Allenby (3-16) troubled the home side and eventually had them bowled out at 145.
In their first innings, Somerset knocked off 107 runs in the deficit with Marcus Trescothick (45 not out) and Chris Rogers (58 not out) going strong.
Leicestershire elected to field first. Even though, Derbyshire lost both their openers early, a 84-run stand between Alex Hughes (55) and Wayne Madsen (38) provided some respite.
Charlie Shreck (3-67) continued to the trouble the Derbyshire batsmen with a three-wicket haul but Harvey Hosein (79 not out) ensured the home side ended the day at 282 for eight.
Glamorgan won the toss and decided to bat first. Despite, Graham Napier's (4-46) four-wicket haul kept the Glamorgan batsmen in check, Kiran Carlson (101 not out) scored a vital century to keep the fight going.
After being 127 for seven at one stage, Carlson shared an unbeaten 129-run stand with Owen Morgan (51 not out) to take Glamorgan to 256 for seven at stumps.
Gloucestershire elected to field first as Northamptonshire lost Ben Duckett (5) early. Rob Newton (130) and skipper Alex Wakely (104) shared a massive 196-run stand for the second wicket to bring the innings on track.
However, Liam Norwell (3-51) and Craig Miles (2-58) dented the momentum of Northamptonshire and had them at 322 for six at the end of the first day.
© Cricket World 2016