Back of a length delivery, top-edgy and as Williamson hit it, you could hear him on the stump mic saying 'oh no!' But it's been a good innings.
WICKET
Williamson c Delany b Little 62 (NZ 174-4)
Good catch!
With wickets in the shed, New Zealand are playing a shot a ball at the moment, and who can blame them.
Kane Williamson tries to pull Josh Little away but it flies off the top edge and Garth Delany gets across well at deep square leg to take a catch on the dive to his right.
Post update
Henry Moeran
BBC Test Match Special commentator
What an important set of boundaries at the end of the McCarthy spell.
NZ 173-3
The wheels have well and truly come off for Ireland.
Kane Williamson follows the six with an upper cut over short third for four, before planting an enormous six over mid-wicket.
He's flying. He's up to 61 off 34 balls now. He's silencing a few people.
Post update
Alex Hartley
Former England bowler on BBC Test Match Special
That's cleared the boundary by a distance. There has been a lot of questions over whether Williamson has batted quickly enough in this tournament. He'll have shut a few people up today.
50 for Williamson
NZ 163-3
Shot!
Kane Williamson gets down on one knee and slog sweeps over mid-wicket to bring up his half-century off 32 balls. He's batted brilliantly.
The catch was taken in the crowd too. Love to see it.
Post update
Alex Hartley
Former England bowler on BBC Test Match Special
Short fine leg is one of the hardest places to take a catch. The ball has been dragged and the fielder has no idea the catch is coming.
Post update
Henry Moeran
BBC Test Match Special commentator
That went reasonably quickly but it should have been taken.
Mitchell dropped on 19
Oh no!
A rank full toss from Barry McCarthy is whipped round the corner by Daryl Mitchell.
It goes just to the left of Josh Little, around belly button height but the ball just pops out of his hands.
Ireland haven't been great in the field today.
Post update
Alex Hartley
Former England bowler on BBC Test Match Special
We often see players with a small towel tucked into their trousers to dry their hands if they get sweaty. Paul Stirling genuinely has a full hand towel - it's down to his knees!
NZ 152-3
Another good over for New Zealand.
But there are loose balls from Ireland creeping in.
Mark Adair offers width to Daryl Mitchell and the Kiwi just smacks it to the cover boundary.
A score of 180-plus is well and truly on here.
Post update
The wicket of Glenn Phillips gave Ireland a chance of restricting New Zealand, but they've bowled a bit loosely since then.
Post update
Henry Moeran
BBC Test Match Special commentator
That was horribly down the leg side. Any batter worth his salt should expect to get four runs off that.
NZ 140-3
I don't want to say anything that is going to come back to haunt me but it feels like New Zealand are just working their way to a total that Ireland won't be able to get near.
Ireland are helping them though with some loose balling. George Dockrell starts with a wayward ball and Kane Williamson punishes it, whipping to the square-leg fence, before he pummels a pull into mid-wicket.
He's up to 42 off 29. He's played nicely.
Post update
New Zealand have shown plenty of power so far.
They look a really good side.
NZ 128-3
Twenty20 cricket is so often about getting out of the over.
Josh Little is unable to do it on this occasion.
He starts the over with five singles, before a wide gives New Zealand an extra ball and Daryl Mitchell sends it to the square-leg boundary.
Post update
Here's how Ireland got the wicket of Devon Conway.
They are chipping away.
NZ 118-3
Good over for Ireland. Just four runs come after the wicket.
They are going to want to squeeze New Zealand and try to restrict them.
WICKET
Phillips c Dockrell b Delany 17 (NZ 114-3)
Gone! This might help restrict New Zealand.
Glenn Phillips was playing like he had a licence to attack and that is more than fair enough with the platform that New Zealand have.
He tries to smash over the off-side again, but picks out George Dockrell at deep cover, who takes a good, low catch coming in off the boundary rope.
A useful 17 off nine balls for Phillips.
Post update
Carl Hooper
Former West Indies all-rounder on BBC Test Match Special
Jeez, Phillips is timing it well. The ball is sounding really good off the bat. This is a man in prime, prime form.
This will also take the pressure off Williamson. He won't need to take any unnecessary risks with Phillips in such good nick.
Live Reporting
Tom Mallows
All times stated are UK
Post update
Alex Hartley
Former England bowler on BBC Test Match Special
Back of a length delivery, top-edgy and as Williamson hit it, you could hear him on the stump mic saying 'oh no!' But it's been a good innings.
WICKET
Williamson c Delany b Little 62 (NZ 174-4)
Good catch!
With wickets in the shed, New Zealand are playing a shot a ball at the moment, and who can blame them.
Kane Williamson tries to pull Josh Little away but it flies off the top edge and Garth Delany gets across well at deep square leg to take a catch on the dive to his right.
Post update
Henry Moeran
BBC Test Match Special commentator
What an important set of boundaries at the end of the McCarthy spell.
NZ 173-3
The wheels have well and truly come off for Ireland.
Kane Williamson follows the six with an upper cut over short third for four, before planting an enormous six over mid-wicket.
He's flying. He's up to 61 off 34 balls now. He's silencing a few people.
Post update
Alex Hartley
Former England bowler on BBC Test Match Special
That's cleared the boundary by a distance. There has been a lot of questions over whether Williamson has batted quickly enough in this tournament. He'll have shut a few people up today.
50 for Williamson
NZ 163-3
Shot!
Kane Williamson gets down on one knee and slog sweeps over mid-wicket to bring up his half-century off 32 balls. He's batted brilliantly.
The catch was taken in the crowd too. Love to see it.
Post update
Alex Hartley
Former England bowler on BBC Test Match Special
Short fine leg is one of the hardest places to take a catch. The ball has been dragged and the fielder has no idea the catch is coming.
Post update
Henry Moeran
BBC Test Match Special commentator
That went reasonably quickly but it should have been taken.
Mitchell dropped on 19
Oh no!
A rank full toss from Barry McCarthy is whipped round the corner by Daryl Mitchell.
It goes just to the left of Josh Little, around belly button height but the ball just pops out of his hands.
Ireland haven't been great in the field today.
Post update
Alex Hartley
Former England bowler on BBC Test Match Special
We often see players with a small towel tucked into their trousers to dry their hands if they get sweaty. Paul Stirling genuinely has a full hand towel - it's down to his knees!
NZ 152-3
Another good over for New Zealand.
But there are loose balls from Ireland creeping in.
Mark Adair offers width to Daryl Mitchell and the Kiwi just smacks it to the cover boundary.
A score of 180-plus is well and truly on here.
Post update
The wicket of Glenn Phillips gave Ireland a chance of restricting New Zealand, but they've bowled a bit loosely since then.
Post update
Henry Moeran
BBC Test Match Special commentator
That was horribly down the leg side. Any batter worth his salt should expect to get four runs off that.
NZ 140-3
I don't want to say anything that is going to come back to haunt me but it feels like New Zealand are just working their way to a total that Ireland won't be able to get near.
Ireland are helping them though with some loose balling. George Dockrell starts with a wayward ball and Kane Williamson punishes it, whipping to the square-leg fence, before he pummels a pull into mid-wicket.
He's up to 42 off 29. He's played nicely.
Post update
New Zealand have shown plenty of power so far.
They look a really good side.
NZ 128-3
Twenty20 cricket is so often about getting out of the over.
Josh Little is unable to do it on this occasion.
He starts the over with five singles, before a wide gives New Zealand an extra ball and Daryl Mitchell sends it to the square-leg boundary.
Post update
Here's how Ireland got the wicket of Devon Conway.
They are chipping away.
NZ 118-3
Good over for Ireland. Just four runs come after the wicket.
They are going to want to squeeze New Zealand and try to restrict them.
WICKET
Phillips c Dockrell b Delany 17 (NZ 114-3)
Gone! This might help restrict New Zealand.
Glenn Phillips was playing like he had a licence to attack and that is more than fair enough with the platform that New Zealand have.
He tries to smash over the off-side again, but picks out George Dockrell at deep cover, who takes a good, low catch coming in off the boundary rope.
A useful 17 off nine balls for Phillips.
Post update
Carl Hooper
Former West Indies all-rounder on BBC Test Match Special
Jeez, Phillips is timing it well. The ball is sounding really good off the bat. This is a man in prime, prime form.
This will also take the pressure off Williamson. He won't need to take any unnecessary risks with Phillips in such good nick.