Finally, Dane Paterson makes the breakthrough with his second wicket of the day.
Coming around the wicket to Dean Elgar, he fizzes one back into the left-hander and clips the top of his off bail.
Matt Critchley emerges to join Jordan Cox after that third-wicket stand of 112.
Post update
Middlesex v Glamorgan 222-2
A lovely stroke from Kiran Carlson to end a Ryan Higgins over. That really is a nice shot.
And four to begin the next Josh de Caires over for Sam Northeast. That is a gimme for a player on 109 not out.
Double Nelson is up for the Welsh county.
Play begins at Headingley
Yorks v Leics 0-0
Finally, the season is up and running in Yorkshire and Ben Coad launches it with a maiden to Leicestershire's Rishi Patel.
Coad did find an edge during his first over, but it looked as though it fell short of the slip cordon.
Post update
Sussex v Northants 28-1
Shot! Fynn Hudson-Prentice is in the attack but his third ball is too full and driven on the front foot by Procter for four.
This is a promising start from the Northants captain, who will be vital for the club's chances of a return to the top flight.
'Robinson looks eager'
Sussex v Northants 23-1
Matt Green
on BBC Radio Sussex
With Ollie Robinson coming down the hill, he looks fully fit and eager to go, which is great for Sussex and England supporters.
It's interesting when you can really see his control with the Kookaburra ball, with the Dukes ball it would swing a lot more.
So you can see Ollie just coming tight to the stumps, just trying to bring his catchers behind the batters into play.
Tea at Edgbaston
Warwks v Worcs 183-2
Another good session for the Pears, albeit without quite as much batting fluency as we saw in the morning session.
A much-needed second wicket of the innings via Will Rhodes, who had Roderick caught at slip.
A shower brings about an early tea interval. Fingers crossed and brollies up.
New ball?
Sussex v Northants 23-1
Now then!
Seales bowls short and leg side to Luke Procter, who swivels round and scoops the ball high over short mid wicket.
A box of replacement balls is being carried on to the field - and Henry Crocombe has made his way into one of the stands to retrieve the original ball.
So no new ball as it turns out.
Two balls later, Procter has four more, driven through cover point.
for Jordan Cox
Notts v Essex 156-2
Rex FeaturesCopyright: Rex Features
It's a good day for players making their Essex debuts!
Jordan Cox has followed Dean Elgar in making a half-century on his first appearance for the county and he gets there in style.
The former Kent player thumps leg-spinner Calvin Harrison over the top for six and then two balls later, pulls him for another boundary to reach the landmark from 76 balls.
Get Involved
#bbccricket
Neville DaIton: Imagine the County Championship will be won by the county that has the least rain during the winter months when the competition is now held. #bbccricket
WICKET Roderick c Yates b Rhodes 68
Warwks v Worcs 180-2
Breakthrough!
Will Rhodes finds lift and a hint of movement off a length.
Gareth Roderick is stuck on the crease and fences the ball to Yates at slip.
Rob Jones to bat next.
Post update
Sussex v Northants 13-1
Procter has his first runs of the season with an immaculate drive through cover off the front foot for four off the bowling of Seales.
Sussex will be pleased with the early wicket of Emilio Gay but the bowlers have offered a bit too much width to offer persistent threat so far.
This is a good over from Ollie Robinson, bowling at a lively pace and with better control, forcing a defensive block from Justin Broad.
Maiden over.
No batting points yet
Middlesex v Glamorgan 203-2
Glamorgan have moved over 200 and this partnership between Sam Northeast and Kiran Carlson for the third wicket is now worth 58.
Just a reminder that 200 does not get a batting bonus point anymore. Teams need to reach 250 before they pick up their first one.
Post update
Notts v Essex 139-2
Dillon Pennington has switched ends now, without success so far - although his bowling has been rather better than figures of 1-56 from 13 overs might suggest.
Very much Essex's session so far as the players take a quick drinks break, with Dean Elgar advancing to 67 and Jordan Cox to 39.
Post update
Warwks v Worcs 180-1
Danny Briggs is back on for his first spell since a solitary over before lunch.
Roderick is well forward, playing into the on side but for no run.
The sixth ball is short and cut to cover point for a single.
'An innings of two halves'
Middlesex v Glamorgan 200-2
Guy Swindells
BBC Radio London
Rex FeaturesCopyright: Rex Features
An innings of two halves really (from Sam Northeast). He raced to his first 50 - 51 balls for his first 50 and 95 for his second.
He changed his game to match the match situation.
Post update
Sussex v Northants 9-1
Four runs to Justin Broad, who seizes on a very full ball from Ollie Robinson and drives down the ground for four.
The ball was in the air for a little while but it was hit very straight and safely enough.
Robinson adjusts his length and JB defends into the off side.
Yorkshire win toss and bowl
Yorks v Leics
The waiting's almost over for the Headingley crowd - and, with Shan Masood winning the toss, they'll get to see Yorkshire bowling first when play finally gets under way at 3.40pm.
England's Harry Brook is down to bat at four for the Tykes, although he may well get a bowl at some stage too.
Rehan Ahmed features for Leicestershire, who also have all-rounder Ben Mike making his second debut for them against the county he's just left.
Kashif Ali punishes Booth
Warwks v Worcs 177-1
Short, wide and scythed over backward point by Ali for the first six of the innings!
The next ball is short and awkwardly deflected to third man via glove and splice for one to bring up a century stand with Roderick off 277 balls.
'Talk about making his mark'
Sussex v Northants 5-1
Andrew Radd
BBC Radio Northampton
A little thin edge from Emilio Gay and John Simpson - talk about making his mark and stamping his authority.
It's a super catch down the legside.
for Sam Northeast
Middlesex v Glamorgan 197-2
Congratulations Sam Northeast! A hundred on the first day of the County Championship - every batter's dream!
He picks up a lovely four off Toby Roland-Jones to get to three figures off 146 balls with 15 boundaries.
Having been named the new Glamorgan red-ball captain, he will be delighted to make a big contribution with the bat to set the example for his colleagues.
Live Reporting
Adam Lanigan, Ben Kosky, Ben Pheazey and Deepak Mahay
All times stated are UK
WICKET: Elgar b Paterson 80
Notts v Essex 170-3
Relief for Nottinghamshire!
Finally, Dane Paterson makes the breakthrough with his second wicket of the day.
Coming around the wicket to Dean Elgar, he fizzes one back into the left-hander and clips the top of his off bail.
Matt Critchley emerges to join Jordan Cox after that third-wicket stand of 112.
Post update
Middlesex v Glamorgan 222-2
A lovely stroke from Kiran Carlson to end a Ryan Higgins over. That really is a nice shot.
And four to begin the next Josh de Caires over for Sam Northeast. That is a gimme for a player on 109 not out.
Double Nelson is up for the Welsh county.
Play begins at Headingley
Yorks v Leics 0-0
Finally, the season is up and running in Yorkshire and Ben Coad launches it with a maiden to Leicestershire's Rishi Patel.
Coad did find an edge during his first over, but it looked as though it fell short of the slip cordon.
Post update
Sussex v Northants 28-1
Shot! Fynn Hudson-Prentice is in the attack but his third ball is too full and driven on the front foot by Procter for four.
This is a promising start from the Northants captain, who will be vital for the club's chances of a return to the top flight.
'Robinson looks eager'
Sussex v Northants 23-1
Matt Green
on BBC Radio Sussex
With Ollie Robinson coming down the hill, he looks fully fit and eager to go, which is great for Sussex and England supporters.
It's interesting when you can really see his control with the Kookaburra ball, with the Dukes ball it would swing a lot more.
So you can see Ollie just coming tight to the stumps, just trying to bring his catchers behind the batters into play.
Tea at Edgbaston
Warwks v Worcs 183-2
Another good session for the Pears, albeit without quite as much batting fluency as we saw in the morning session.
A much-needed second wicket of the innings via Will Rhodes, who had Roderick caught at slip.
A shower brings about an early tea interval. Fingers crossed and brollies up.
New ball?
Sussex v Northants 23-1
Now then!
Seales bowls short and leg side to Luke Procter, who swivels round and scoops the ball high over short mid wicket.
A box of replacement balls is being carried on to the field - and Henry Crocombe has made his way into one of the stands to retrieve the original ball.
So no new ball as it turns out.
Two balls later, Procter has four more, driven through cover point.
for Jordan Cox
Notts v Essex 156-2
It's a good day for players making their Essex debuts!
Jordan Cox has followed Dean Elgar in making a half-century on his first appearance for the county and he gets there in style.
The former Kent player thumps leg-spinner Calvin Harrison over the top for six and then two balls later, pulls him for another boundary to reach the landmark from 76 balls.
Get Involved
#bbccricket
Neville DaIton: Imagine the County Championship will be won by the county that has the least rain during the winter months when the competition is now held. #bbccricket
WICKET Roderick c Yates b Rhodes 68
Warwks v Worcs 180-2
Breakthrough!
Will Rhodes finds lift and a hint of movement off a length.
Gareth Roderick is stuck on the crease and fences the ball to Yates at slip.
Rob Jones to bat next.
Post update
Sussex v Northants 13-1
Procter has his first runs of the season with an immaculate drive through cover off the front foot for four off the bowling of Seales.
Sussex will be pleased with the early wicket of Emilio Gay but the bowlers have offered a bit too much width to offer persistent threat so far.
This is a good over from Ollie Robinson, bowling at a lively pace and with better control, forcing a defensive block from Justin Broad.
Maiden over.
No batting points yet
Middlesex v Glamorgan 203-2
Glamorgan have moved over 200 and this partnership between Sam Northeast and Kiran Carlson for the third wicket is now worth 58.
Just a reminder that 200 does not get a batting bonus point anymore. Teams need to reach 250 before they pick up their first one.
Post update
Notts v Essex 139-2
Dillon Pennington has switched ends now, without success so far - although his bowling has been rather better than figures of 1-56 from 13 overs might suggest.
Very much Essex's session so far as the players take a quick drinks break, with Dean Elgar advancing to 67 and Jordan Cox to 39.
Post update
Warwks v Worcs 180-1
Danny Briggs is back on for his first spell since a solitary over before lunch.
Roderick is well forward, playing into the on side but for no run.
The sixth ball is short and cut to cover point for a single.
'An innings of two halves'
Middlesex v Glamorgan 200-2
Guy Swindells
BBC Radio London
An innings of two halves really (from Sam Northeast). He raced to his first 50 - 51 balls for his first 50 and 95 for his second.
He changed his game to match the match situation.
Post update
Sussex v Northants 9-1
Four runs to Justin Broad, who seizes on a very full ball from Ollie Robinson and drives down the ground for four.
The ball was in the air for a little while but it was hit very straight and safely enough.
Robinson adjusts his length and JB defends into the off side.
Yorkshire win toss and bowl
Yorks v Leics
The waiting's almost over for the Headingley crowd - and, with Shan Masood winning the toss, they'll get to see Yorkshire bowling first when play finally gets under way at 3.40pm.
England's Harry Brook is down to bat at four for the Tykes, although he may well get a bowl at some stage too.
Rehan Ahmed features for Leicestershire, who also have all-rounder Ben Mike making his second debut for them against the county he's just left.
Kashif Ali punishes Booth
Warwks v Worcs 177-1
Short, wide and scythed over backward point by Ali for the first six of the innings!
The next ball is short and awkwardly deflected to third man via glove and splice for one to bring up a century stand with Roderick off 277 balls.
'Talk about making his mark'
Sussex v Northants 5-1
Andrew Radd
BBC Radio Northampton
A little thin edge from Emilio Gay and John Simpson - talk about making his mark and stamping his authority.
It's a super catch down the legside.
for Sam Northeast
Middlesex v Glamorgan 197-2
Congratulations Sam Northeast! A hundred on the first day of the County Championship - every batter's dream!
He picks up a lovely four off Toby Roland-Jones to get to three figures off 146 balls with 15 boundaries.
Having been named the new Glamorgan red-ball captain, he will be delighted to make a big contribution with the bat to set the example for his colleagues.