Marcus Trescothick hit a club record 50th first-class century for Somerset as they drew with Warwickshire in Taunton.
Hampshire slumped to 18-5 - losing five wickets for no runs in 17 balls - as Essex ran riot in their Specsavers County Championship match.
Alastair Cook continued his outstanding early-season form while there was an injury scare for James Anderson.
Essex and Worcestershire discovered their prospective semi-final opponents early after a rain-hit final round of South Group fixtures.
James Vince's 178 for Hampshire proved in vain as they slipped to a three-wicket defeat to Glamorgan in the RL One-Day Cup.
Alastair Cook's century helped Essex to a tense 10-run victory over Sussex in the RL One-Day Cup despite a Jerome Taylor hat-trick.
Lancashire won their first game of the Royal London One-Day Cup as Steven Croft's stunning 127 helped them beat Warwickshire.
Billy Root's maiden limited-overs century helped Nottinghamshire to a 10-run Royal London One-Day Cup win over Warwickshire.
Jonny Bairstow scored a career-best 174 as Yorkshire cruised to a target of 336 to beat Durham by six wickets at Headingley.
Gloucestershire claimed an improbable Royal London One-Day Cup win over Middlesex on Sunday, as Somerset and Surrey also won.
Sam Hain struck an unbeaten 89 as Warwickshire began their Royal London One-Day Cup defence with a 10-wicket win at Northampton.
Promising legspinner Mason Crane "needs to play" and might have to move county, says Sky Sports' Nasser Hussain.
Rob Key previews the Royal London One-Day Cup with Warwickshire looking to defend their crown as the white-ball season begins.
Lancashire clinched a comeback win over Somerset on day four of their County Championship clash, skittling the visitors for 130.
The 2017 Royal London One-Day Cup starts on Thursday, test your knowledge on the tournament with our 10-question quiz...
Liam Livingstone starred for Lancashire while Gary Ballance held Hampshire up in their County Championship Division One victory bid.
Joe Root and Jonny Bairstow registered single-figure scores as Yorkshire's top order capitulated against Hampshire at the Ageas Bowl.
New England captain Joe Root returned to action for Yorkshire at Hampshire,
where home skipper James Vince hit a century.
Joe Root will play his first innings in England since being appointed Test captain when Yorkshire take on Hampshire.
Tim Southee has signed for Middlesex for their NatWest T20 Blast campaign.