Bryson DeChambeau and Hideki Matsuyama both miss makeable birdie putts on the par-four 17th.

They do seem to be playing a little quicker than normal, perhaps trying to make sure they complete round one before darkness falls.

Richard Bland is on the 18th green, 20 feet up the hill and that's a good two-putt par to finish.

It took him 478 events to win on the European Tour, but that victory earned him his US Open shot this week. The Englishman was three under at one point but two bogeys checked his momentum.

Four closing pars though means he will sign for a terrific one-under-par 70,

Lee Westwood and Paul Casey enjoy a chuckle on the 8th green, their penultimate hole.

Nice to see they can find humour in the situation after both narrowly missed birdie putts.

"It's still moving," says Louis Ooosthuizen, wistfully, as his approach to the sixth green just won't slide down the ridge like he hoped it would. Still moving, but not enough.

He will have a birdie putt for the outright lead but it's a long one.

Now then Rory, what have you done here? McIlroy almost airmails the 15th green, his ball bouncing on the back and careering into the rough. But that's a sublime chip, nestling up to within a couple of feet.

Dustin Johnson was long and left but stayed on the green. A great lag putt from 45 feet to within two sees the American remain at level par.

Bryson DeChambeau plays a little chip and run out of the rough on the 16th and does one of those little jumps in the air when he thinks his ball might just curl in.

It's too speedy to take the break though and he's off mumbling to himself.

Hideki Matsuyama for birdie from 10 feet. No dice. Both walk off with pars.

Lee Westwood is millimetres away from moving two under with a putt that just slides ever so slightly to the right. Unlucky.

Jon Rahm, on two under, is a hole behind but has found a bunker next to the sixth green. A delicious shot from the sand rescues a certain par though.

We have a new co-leader.

Louis Oosthuizen has had a lot of looks at birdies on the back nine but none have been easy.

He finally makes one count, though, and the South African draws level with Russell Henley on four under at the top of the leaderboard.

It's a game of fractions is golf. And Bryson DeChambeau is a fraction short with his tee shot on the par-three 16th. And that fraction means he's in the rough, rather than on the putting surface.

Hideki Matsuyama does get it right though and he's got a birdie look from 10 feet.

If this group gets a wriggle on they might just make it in before San Diego sundown. Or Stockport sunrise, as it will be for me ever-so shortly!

Rory McIlroy hit a great tee shot down the 14th fairway but was a little short with his second, leaving a lengthy birdie putt, which he knocks three feet by.

Justin Rose doesn't often show much emotion on a golf course but another missed putt sees him gesticulate and walk away chuntering to himself. Thankfully, that was a birdie putt, so although no shot gained, there's no shot dropped either.

Dustin Johnson also safely in for par.

Lee Westwood took advantage of that birdie chance on the 6th green but Paul Casey did not.

Westwood moves within three of the lead - could he... no, no, let's not get carried away.

"Oh my god!" shouts Bryson DeChambeau as his second shot on the 15th soars to the back of the green.

He'll have a 45ft putt for a birdie.

Four holes of the opening round left for Lee Westwood and Paul Casey - and both Englishmen have landed lovely shots onto the 6th green.

Both are on level par - can they make a move on their way into the clubhouse?

We've seen nothing of the progress of world number one Dustin Johnson down this 13th hole. But he has found the first cut just off the green in two, and then chipped up to a couple of feet for a simple birdie to get back to level par

Rory McIlroy, meanwhile, is made to pay for that poor second shot that stayed in the rough. It's a bogey.

Rory McIlroy gouges his third out of the thickest of rough. The ball is not visible, and neither are Rory's shoes.

No going for the flag from there, it's just get the ball on the green and hopefully walk off it with a two-putt par.

Work to do though - he's about 40 feet from the hole. And that's an awful putt. The ball pulls up a good 15 feet short.

Perhaps I shouldn't have published that stat about how great he is on the par fives over the past decade!

That's impressive for Bryson DeChambeau.

His whole week could have easily gone down the toilet after three bogeys in a row, but he's dug deep and is rewarded with a birdie on the 14th.

It's only Thursday, all is not lost.

Phew. Jordan Spieth gets a handle on things with a first birdie of the day on his 13th.

After bogeying his 12th, he goes straight down the middle and sinks a 19ft putt to get back to two over.

Fellow American Scottie Scheffler birdies too and he's back to level par.

Rory McIlroy tugs his tee shot on the 13th way left. His back foot slipped just before he hit the ball. Still, it's a par five so that may play into his hands.

Repeat after me... A nice simple wedge out into the fairway. A nice simple wedge out into the fairway...

A nice simple wedge into the rough... Rory, Rory, Rory. I'm as disappointed in you as you are in yourself with that shot.

Russell Henley remains in the lead on four under, then.

Several players have threatened to join him over the past couple of hours but none have managed it.

Louis Oosthuizen was the latest to have that chance but was just off target with a mid-distance birdie opportunity.

Bryson DeChambeau has truly unravelled on the par-five 13th.

It started out with a perfect drive, but his second shot came up short and ended up in a divot. From that horrible lie, he took a trip to a bunker.

From there it was into the rough off the back of the green. A two-putt gives the defending champion another bogey and puts him eight shots off the lead.