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England all-rounder Ben Stokes claimed two wickets on his return to action for the first time since his chastening experience in the final over of the ICC World Twenty20 final.
The 24-year-old removed Australia batsman Adam Voges and James Harris, the former for 50, en route to figures of two for 66 against Middlesex on his first Specsavers County Championship appearance of the season for Durham.
Stokes' first over was a maiden and it took 61 balls to concede the 24 runs that came from just four deliveries at the hands of Carlos Brathwaite during England's heartbreaking defeat to the West Indies in India earlier this month.
Middlesex enjoyed the better of the opening day at the Emirates Riverside, though, advancing to 358 for seven at the close following half-centuries from Nick Gubbins and Dawid Malan.
Gary Ballance enhanced his prospects of joining Stokes in the England Test side again this summer with an unbeaten 50 as champions Yorkshire were made to work hard by Warwickshire at Edgbaston.
The left-hander, dropped during last year's successful Ashes campaign, stopped the hosts in their tracks after the White Rose were reduced to 85 for four.
Ballance was well supported by Jack Leaning, who also made 50 not out in a stand of 92 to lead Yorkshire to 177 for four when bad light stopped play.
Kumar Sangakkara compiled the innings of the day, hitting a magnificent 171 from 176 balls to help Surrey dominate Somerset at the Oval.
The veteran Sri Lankan struck 24 fours and a quartet of sixes, moving to three figures from just 94 deliveries, and shared a second-wicket stand of 187 with Rory Burns.
Burns contributed 80 and England limited-overs batsman Jason Roy blazed 85 to propel Surrey to 394 for five.
In Division Two, England Test skipper Alastair Cook continued his preparations for the international summer with a half-century for Essex against Northamptonshire at Chelmsford.
Cook added 65 to his back-to-back tons in the third of four appearances for his county ahead of England's Test series with Sri Lanka, starting next month.
England hopefuls Nick Browne and Tom Westley made 60 and 64 respectively before Ravi Bopara and Dan Lawrence, with 57 and 44 respectively, led Essex to 335 for three.
England spinner Moeen Ali failed to take a wicket during eight overs of off-spin on his return to county duty as Hamish Marshall's unbeaten 123 and 84 not out from Kieran Noema-Barnett made Worcestershire regret their decision to bowl at Bristol.
After Chris Dent passed 5,000 first-class runs in making 59, Marshall and Noema-Barnett's unbroken sixth-wicket stand of 179 guided Gloucestershire to 336 for five.
Former England Under-19 international Daniel Bell-Drummond's 124 helped Kent recover from 105 for five to reach 227 for seven against Leicestershire at Grace Road.
Will Bragg was dismissed lbw by Wes Durston late on for 129 of Glamorgan's 308 for six against Derbyshire at Derby.