Cameron Bancroft blasted an unbeaten century on his List A debut for Durham to reward the club for their faith in him as they opened their Royal London One-Day Cup campaign with a 72-run win over Northamptonshire.
The 26-year-old Australia batsman, who was suspended for nine months after being caught up in last year's ball-tampering scandal, hit an unbeaten 151 from 130 deliveries.
Bancroft shared a record-breaking fourth-wicket stand with Michael Richardson, who also notched a century to set Northants a daunting target of 343 to chase.
Jason Holder (86) and Alex Wakely (66) put forward impressive efforts with the bat for the visitors but Matt Salisbury (three for 51) and Matthew Potts (four for 62) held their composure with the ball to guide the north east side over the line to get off the mark in the 50-over format.
Gary Ballance and Harry Brook hit superb centuries as Yorkshire got their campaign off to a winning start by 213 runs against Leicestershire.
The pair shared a match-turning fourth-wicket partnership of 211 as the Tykes made 379 for seven and the Foxes never looked like chasing it down at Emerald Headingley.
Leicestershire got off to the perfect start when seamer Tom Taylor (three for 57) removed Adam Lyth for a third-ball duck and David Willey and Tom Kohler-Cadmore cheaply as the Vikings, invited to bat, slipped to 17 for three inside five overs.
But Ballance hit a career-best 156 off 133 balls, his third century in three innings to start the season, and 20-year-old Brook posted his maiden List A century with 103 off 105 balls.
In reply, Leicestershire fell to one for one after four balls and were bowled out for 166 inside 30 overs as Mathew Pillans claimed a maiden five-wicket haul with figures of five for 29 from 6.3 overs and the Foxes suffered their heaviest defeat, runs-wise, against county opposition.
Hamish Rutherford and Daryl Mitchell hit their second centuries of the season as 2018 semi-finalists Worcestershire got this year's campaign off to a winning start with a 125-run victory over Lancashire.
Rutherford celebrated his List A debut for Worcestershire with a ton and Mitchell stroked his fourth hundred in seven innings against Lancashire at Emirates Old Trafford.
The Rapids, who have topped the North Group in this competition in each of the past two seasons, confirmed their status as one of the most powerful white-ball sides in the country by making 367 all out in 49.1 overs.
In reply, Lancashire, wearing a new blue strip, made 242 all out in 40.4 overs.
Chris Liddle and Tom Smith claimed three wickets each as Gloucestershire skittled Surrey for just 88 to win by 147 runs.
The home side were bowled out for 235 after winning the toss, having been 156 for one, with Chris Dent (75) and Gareth Roderick (74) the main contributors.
Rikki Clarke finished with four for 43 and Tom Curran three for 26.
It looked a below-par total but Surrey turned in a hapless batting display, Jason Roy top-scoring with 19 as they were bowled out in only 24 overs.
Liddle finished with three for 17 and left-arm spinner Smith three for seven from two overs.
Essex completed a resounding 180-run victory over Glamorgan in their clash at Sophia Gardens.
The visitors posted an imposing 326 for seven off their 50 overs, with opener Varun Chopra scoring 111, supported by 50s from Tom Westley and Dan Lawrence, while Sir Alastair Cook struck 40.
In reply, Glamorgan were skittled out for 146 in just 31 overs, with Ravi Bopara the pick of the Essex bowlers as he took three for 26 from seven overs.
Sam Northeast struck an unbeaten century to steer Hampshire to an emphatic 90-run win against his former county Kent.
In a replay of last year's final that Hampshire won by 61 runs, they made good use of a decent batting surface to post 310 for nine.
Chris Wood, Kyle Abbott and Liam Dawson then claimed two wickets each as Kent never recovered from slipping to 35 for three and were finally dismissed for 220.
