Commentary of every game available at top of this page
All 18 counties split into three regional groups of six
Each side will play five games
Two sides with most points play five-day final
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Nottinghamshire 13-1 v Yorks 264 all out
Chris Nash's perfect day ends on a sour note as he's bowled by Steven Patterson.
And that'll be the last action at Trent Bridge today too.
Gloucestershire 182-8 (Warks)
Four overs remaining at Bristol. Number nine and ten Tom Smith (8) and Josh Shaw (0) are still in at the crease.
We've seen a lot of starts in Gloucestershire's innings but only Ben Charlesworth has made it past 50.
Northants 67 v Somerset 166
And the Northants first innings is over in a flash...
Craig Overton gets one through last man Brandon Glover to finish with 4-12.
Incredibly, Somerset have a lead of 99.
Sanderson c&b C Overton 0 (Northants 67-9 v Somerset 166)
The Northants collapse continues...
Ben Sanderson pokes one back to Craig Overton and the giant seamer clings onto a fine low catch.
67-9, all sorts of bother.
Liam Livingstone gets in on the wickets as Durham number 11 Chris Rushworth edges to the keeper.
The hosts finish on 180, Lancashire will now have to survive a tricky nine overs before close of play.
Berg c Hildreth b J Overton 0 (Northants 67-8 v Somerset 166)
Things go from bad to worse for Northants.
Gareth Berg tries to leave one from Jamie Overton but the ball clips the toe of the bat and flies to slip where James Hildreth takes a fine diving catch.
Northants look set to concede a big first-innings lead in the context of this game. They trail by 99.
Essex 247-6 v Surrey
Well batted Adam Wheater.
The Essex wicketkeeper brings up his half-century off 94 balls.
Not long to go on day one at Chelmsford now.
Image source, Rex FeaturesDurham 177-9 v Lancs
There's also a wicket for Lancashire's Richard Gleeson who hits Matthew Salisbury on his toe and it's given lbw.
A cracking yorker that and Durham are now nine down.
We've still got another 12 overs to go at Chester-le-Street.
Worcs 295-3 v Glamorgan
A tough day in the dirt for Glamorgan as Jake Libby and Brett D'Oliveira bat on and on at New Road...
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Kent v Sussex 284-8
Speaking of youngsters, Kent spinner Marcus O'Riordan has just claimed his third Sussex wicket.
He pins Henry Crocombe lbw.
Middlesex 252 v Hants 5-0
Joe Weatherley and Felix Organ are opening for Hants. Plenty of youngsters getting a go in these five rounds of the Bob Willis Trophy while all the international cricket is squeezed in also.
Nice to see.
Notts 6-0 v Yorks 264
Right, a minimum of six overs remain for Nottinghamshire today. How do they approach this?
On the front foot it seems as Chris Nash, fresh from his unlikely bowling heroics, creams one to the ropes.
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Worcs 280-3 v Glamorgan
Century number two for Worcestershire.
Brett D'Oliveira joins Jake Libby (133*) in the hundred club at New Road as Glamorgan continue to toil.
Their fourth-wicket partnership is worth 210 and growing.
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Northants 67-7 v Somerset 166
It's all going wrong for Northants.
Captain Adam Rossington has just been dismissed, edging a beauty from big Craig Overton behind.
Gareth Berg and Ben Sanderson, both on nought, are at the crease. Northants trail by 99.
Scott lbw b Hannon-Dalby 17 (Gloucestershire 178-8 v Warks)
That's wicket number four for Warwickshire's Oliver Hannon-Dalby.
The medium-fast bowler traps George Scott lbw for 17.
Gloucestershire are 178-8 with 11 overs remaining in the day.
Durham 165-8 v Lancs
Liam Hurt has deserved a wicket today and he finally gets one.
He entices a pull from Brydon Carse which goes straight to Dane Vilas who takes an excellent low catch at square leg.
Carse goes for 11 off 35 deliveries.
Notts v Yorkshire 264
Jordan Thompson will rightly get most of the plaudits at Trent Bridge today but what about Chris Nash?
The opening batsman - and part-time spinner - hadn't bowled a delivery in first-class cricket for over two years before today.
He finishes the innings with figures of 3-20 from 6.2 overs.
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Middlesex 252 v Hants
Middlesex's first innings folds quickly at Radlett.
Liam Dawson claims the final wicket, as he snaffles Tom Helm off his own bowling.
The last three wickets fell in the space of eight balls.
14 overs left for Hampshire to bat tonight.
Thompson c Mullaney b Nash 98 (Yorkshire 264 all out v Notts)
Image source, Rex FeaturesNoooooooooo!
Sometimes I really hate cricket.
In just his fourth first-class appearance it looked like Jordan Thompson was certain to get his maiden century.
He'd farmed the strike brilliantly, smashed 11 fours and four sixes.
On 98 he goes for the big shot but gets is all wrong and Steven Mullaney easily gathers at slip.
Still, a great total for Yorkshire considering they were 44-4 this morning.
Walter b Borthwick 33 (Essex 222-6 v Surrey)
Scott Borthwick provides the breakthrough Surrey needed!
The spinner gets one through Paul Walter and breaks a gutsy stand with Adam Wheater.
Who's on top at Chelmsford? No idea now.