Stuart Broad and James Anderson on opposite sides as Notts bowl out Lancashire for 214.
Surrey's Gus Atkinson takes 6-68 - his first five-for - for 2022 champions against Essex.
Second-placed Hampshire all out for 229 on day one against Warwickshire.
Australia batter Steve Smith makes debut for Sussex at New Road
Jonny Bairstow takes three catches behind stumps for Yorkshire against Glamorgan.
On-loan paceman Henry Brookes takes 6-20 on debut for Derbyshire.
Hampshire 83-2 v Warwickshire
12 minutes early due to the early lunch, we are back!
Chris Woakes finishes the over he began by ousting Nick Gubbins. James Vince gets off the mark from his first delivery of the afternoon session. Fletcha Middleton remains at the other end on 45 and whips Woakes through mid-wicket for another four.
Image source, Rex FeaturesWith the Coronation of HRH King Charles III just two days away, we thought we'd re-introduce you to an appropriately-named West Indies all-rounder, who made his Test debut in England in 1976, helping Clive Lloyd's side to a 3-0 series win.
He surpassed that by hammering 86 of 66 balls in the 1979 World Cup final at Lord's and sharing a stand of 139 with Viv Richards, who hit an unbeaten 138.
His official international career came to an end after he went on two 'rebel' tours to South Africa.
King once hit 74 sixes in a season with Welsh village side Pontblyddyn and played for Yorkshire club Dunnington into his 60s.
Yorkshire v Glamorgan 83-2 - lunch
Nick Webb
BBC Radio Wales
Jonny Bairstow had just the start he was hoping for on his return from an eight-month first-team absence with a simple catch provided from the edge of David Lloyd’s bat fourth ball after Adam Lyth chose to bowl first.
Ben Coad snapped up his second wicket in his third over as Andrew Salter, doing emergency opening duty after Eddie Byrom woke up with a back spasm, was trapped lbw also without scoring.
Bairstow showed his confidence when choosing to stand up to the wicket against Coad to restrict Marnus Labuschagne's footwork, while Sam Northeast should have been back in the pavilion for nine when Lyth dropped a simple slip chance off Matthew Fisher.
Labuschagne dug in, leaving frequently, but Yorkshire thought they had him caught behind off Mickey Edwards for 10 only for the confident appeal to be turned down.
Northeast, trying to regain form after a lean spell, dominated the scoring, reaching 49 not out as Glamorgan earned parity by lunch.
Somerset v Northants 108-1 - lunch
Anthony Gibson
BBC Radio Somerset
Very much Northamptonshire's morning as Somerset's seamers failed to make the most of a green-looking pitch.
A dropped catch in the first over - Tom Kohler-Cadmore at first slip the culprit - didn't help, and Ricardo Vasconcelos has been only too happy to make the most of the plentiful loose deliveries that have been on offer.
Craig Overton has been unlucky, not just in the matter of the dropped catch, but also in several other nicks that haven't gone to hand. He cut a deeply frustrated figure as the players went off for lunch.
Notts v Lancs 118-5
Dave Bracegirdle
BBC Radio Nottingham
In football parlance this has been a game of two halves so far. For the opening hour Lancashire, put in, romped along at five runs an over and at 80-1 were threatening to take the contest away from the hosts.
Things turned around after midday, Brett Hutton dismissed Dane Vilas first ball and ended the session with his third wicket, that of George Bell, to balance things out.
The Red Rose have Josh Bohannon to thank for their flying start and he remains at the crease with 61 from only 60 balls, with nine fours.
Image source, Getty ImagesAs Jonny Bairstow continues his recovery from a broken leg by playing for Yorkshire's first team we want you to pick your England team for the first Ashes Test.
Head coach Brendon McCullum has said there is "no doubt" that Bairstow comes back into the team when fully fit, but where does he fit in?
His replacement Harry Brook averages 80.90 after his first six Tests so a straight swap may not be the way England go.
Does Bairstow replace Ben Foakes behind the stumps? Does he come in for Zak Crawley at the top of the order?
Tough decisions, and that is before you've even thought about your bowling attack!
Division One
Essex 100-2 v Surrey
Hampshire 83-2 v Warwickshire
Nottinghamshire v Lancashire 118-5
Somerset v Northamptonshire 108-1
Division Two
Derbyshire v Leicestershire 77-6
Worcestershire 111-5 v Sussex
Yorkshire v Glamorgan 83-2
Derbyshire v Leicestershire 77-6
Quite a morning for Warwickshire's Henry Brookes, who began life on loan at Derbyshire by taking two wickets in an over - twice.
He has 4-6 from six overs, and with Luis Reece also claiming a couple of victims, the home side will be hoping to clear up the Leicestershire lower order during the afternoon.
Rehan Ahmed is 22 not out, with Tom Scriven on three.
Somerset v Northamptonshire 108-1
108-1 in 28 overs. Goodness.
The drop of Hassan Azad by Tom Kohler-Cadmore off Craig Overton in the opening over feels like a big moment. The hosts could have taken early charge but as it is they let Northants get away and it has been far too comfortable for the batters in what look like bowler-friendly conditions.
Lunch chat will be interesting in the Somerset ranks.
Yorkshire v Glamorgan 83-2
When you’re 1-2 in the fifth over and you're looking for a couple of batters to come in and steady the ship, there aren’t too many in county cricket you would choose ahead of Marnus Labuschagne and Sam Northeast.
After Ben Coad had removed both openers without scoring, the Glamorgan pair have put on an unbroken stand of 82 for the third wicket, helping the visitors to 83-2 at lunch at Headingley.
Northeast needs one more for a half-century, what would be his first of the season so far.
The returning Jonny Bairstow took a routine catch behind the stumps to remove David Lloyd in the first over.
Worcestershire 111-5 v Sussex
Ged Scott
BBC Sport at New Road
Sussex‘s morning in Worcester - and Ollie Robinson‘s in particular.
Four wickets in his first seven-over spell, followed by a further three overs in a second spell sent down just before lunch.
Encouraging news for England - and Sussex, who still have a further two games‘ use out of Robinson before international duty calls again.
But Worcestershire have made an encouraging recovery in the three quarters of an hour before the interval.
Somerset and Warwickshire old boy Adam Hose, making only his second Championship appearance, has looked untroubled in turning things round with an unbeaten 46 in a 67-run stand with Gareth Roderick (20).
Essex 100-2 v Surrey
Nick Gledhill
BBC Essex
What could be a pivotal moment here just before lunch, with Alastair Cook being brilliantly caught by Ben Foakes down the leg side off Gus Atkinson.
Cook had looked set for a big score, having been dropped on 13 he had prospered on a good pitch against a strong Surrey attack finding some swing.
He reached his first fifty of the season with a trademark cover driven four off Kemal Roach. An eventful innings then saw him survive a hard chance to second slip before Atkinson struck.
It has been a good morning for the Surrey seamer who earlier removed Nick Browne with just his second ball to break the opening stand at 62 and with Cook’s dismissal Surrey will sense an opportunity.
Somerset v Northamptonshire 107-1
Brought up by you-know-who via a you-know-what. He's onto 56.
Sam Whiteman then slashes at a wide one from countryman Peter Siddle but his edge flies between second and third slip and away to the boundary.
Somerset have had a pretty miserable morning session.
Notts v Lancs 118-5
Nottinghamshire will feel a lot better about their morning’s work after three wickets late in the morning session at Trent Bridge.
Brett Hutton makes another breakthrough on the brink of lunch, George Bell edging to Ben Duckett at slip.
Lancashire scored pretty freely throughout the session, led by Josh Bohannon’s unbeaten 61, but having been 109-2 they have reached the interval at 118-5.
Hutton has taken 3-32, while Stuart Broad had Steven Croft caught behind for his only wicket of the morning.
Worcs 106-5 v Sussex
Adam Hose is leading the Worcestershire recovery at New Road after four wickets by Ollie Robinson helped reduce them to 44-5.
A square drive and off drive, both for four, off Sean Hunt are followed by another as the left-armer drops short and is pulled away.
Hose is now 42 not out and Gareth Roderick has 19.
Somerset v Northamptonshire 99-1
Another sumptuous cover drive from the southpaw brought up his 10th four and the 25-year-old moves to 50 in the next over, taking Peter Siddle within inches of the rope to run three.
It's been firmly Northants' morning and Vasconcelos brings up his 18th first-class century from 72 balls. It's been a very comfortable morning for him, if truth be told.
Hampshire 83-2 v Warwickshire
Common sense is the winner. We'll see what the sky is doing in 40 minutes time.
That wicket just about restores parity in the morning session. Without it you'd have to say Hampshire had made a flying start.
Essex 95-2 v Surrey
Image source, Rex FeaturesThat is why Ben Foakes is England's top gloveman.
Gus Atkinson finds the inside edge of Alastair Cook's bat and Foakes flings himself full length across to the leg-side to take a brilliant one-handed catch.
So, no addition for Cook after being dropped for the second time. Dan Lawrence comes out for the final few minutes before lunch.
Hampshire 83-2 v Warwickshire
James Vince strode out but never made it to the square. There is a lot of cloud and gloom and clearly some precipitation too... the umpires have opted to take the players off. How frustrated Nick Gubbins must be.
You'd hope this will be an early lunch to save time later.
Essex 95-1 v Surrey
Dropping Alastair Cook once is never wise. Doing it twice could prove very costly indeed.
Kemar Roach finds the edge but Ollie Pope cannot hang onto a diving slip chance and the Essex opener takes a single to move to 51 not out.