A fantastic finish from Russell Henley, who nails a five-footer right into the middle of the hole to post an opening round of 67 for the clubhouse lead as it stands.

Marcus Armitage speaking to Sky Sports:

"The win [in Hamburg] gives you confidence but straight away you dismiss it and think 'let's see if I can perform at Major level now'. That's just the natural competitor in me.

"But it has given me more confidence, as does competing in fields like this.

"It's a tough start on 10 and 11, quite a long par three, then 12 which I think the last time they played the US open here, it played the toughest hole."

Phil Mickelson's birdie putt starts too far left and although it curls round late on, it's always going wide. "Stop, stop," Mickelson implores his ball as it slides off down a slope, three, four, five feet.

This round is in danger of getting away from Phil. Another missed putt. Another shot gone.

Xander Schauffele tidies up for par.

Like his older brother, Francesco Molinari has been steady on the back nine. And after a run of eight straight pars, the Italian claimed a birdie on the par-three 16th after hitting his tee shot within 21 feet.

Tommy Fleetwood is playing his third shot into the 623-yard par-five ninth hole from the middle of the fairway, suggesting he laid up. It's about a 6/10 shot though. Not troubling the flag.

What can Matthew Wolff conjure up from 100 yards? He's pin-high, 10 feet to the left.

Fleetwood up first, from 25 feet. Decent putt to a couple of feet. Par and a round of one-over 72.

Wolff for a ninth birdie of the round...not this time. Par finish and a one-under 71.

Iain Carter
Radio 5 Live commentator

If you click on the link on this page, or tune your digital radio into BBC Radio 5 Live Sports Extra you can listen to live commentary of this opening round of the US Open.

"Sit, sit." It can only be Phil Mickelson as he carves another ball through the Californian sky and into the guts of the seventh green.

The ball obeys. Outside birdie chance coming up.

Xander Schauffele is in the rough down the left and his ball stays left, pulling up short of the green. Most of us amateurs would be chipping and running from there. Not Xander. Wedge with plenty of loft in hand, clips the ball skywards and gets it stop a foot past the hole. Beautiful to watch.

What a day for Marcus Armitage. Playing in just his second major, the 33-year-old Englishman has gone round in a level-par 71.

The world number 122 threatened a couple of early birdies before making a couple stick either side of the turn. They may have been swiftly cancelled out by two bogeys but there were a couple of hard-earned par saves, including an 11-foot putt on his final hole, and he showed his satisfaction with a fist pump. Not a bad day's work by the Yorkshireman.

Image source, EPA

The par threes have really caught this group out - they all dropped a shot on the third early on the back nine and now Collin Morikawa and Justin Thomas do the same again.

Poor putting from both to blame - but not Brooks Koepka, who rescues a par from a tee shot that found the bunker with two cracking shots.

A par five final hole to come - can Brooks finish big?

Phil Mickelson is dropping a shot on the par-four sixth after pushing his approach into the rough surrounding the green.

He chipped out nicely to five feet but tugged his par putt left.

Xander Schauffele is rattling along nicely though. A four-foot par putt sees him stay just one off the lead.

All of a sudden, it's all going a bit wrong for Brooks Koepka.

Four under after 11 holes, he's dropped two shots since - and has now hit the bunker at the front of the green on the par-three eighth, this group's penultimate hole of the day.

Tommy Fleetwood's radar is a little off on the par-three eighth. He's found the back of the green with his tee shot but starts his 30-foot putt out to the right and it stays there, wandering about five feet wide.

Matthew Wolff came up short in a bunker. He knows he's played a decent shot though and scurries out of the sand to see just how close he's hit his ball. About three feet is what he finds.

Both save par and move on to the ninth, their final hole of this opening round.

Francesco Molinari made a positive start at Torrey Pines, but his older brother Edoardo has crept under the radar on the back nine.

After dropping a shot at the 11th, the Italian bounced back by making putts from over 23 feet and then 28 to birdie the 13th and 14th holes, respectively, and join Francesco on one under.

Edoardo came in with four straight pars to finish his round, and with it being tight at the top of the leaderboard, that should be enough to put him in contention for day two.

A poor tee shot and a short chip leave Brooks Koepka too much to do and he is unable to rescue par from the edge of the green.

Pars for Justin Thomas and Collin Morikawa, although the latter is unlucky to see a birdie putt just slip past.

Image source, Getty Images

Tommy Fleetwood is scrambling on the par-four seventh, his 16th hole of the day.

A pulled drive means he can't reach the green in two. But his third is majestic, bouncing a yard short of the hole and immediately putting the brakes on. Tap-in par.

Matthew Wolff's up and down round is continuing though. From the middle of the fairway, he pushes his second way right, hitting a tree and startling a ball spotter who was sitting under the Torrey Pine, presumably thinking a professional golfer would hit the green from 150 yards out.

A hack and a chip and two putts later and Wolff is signing for a six.

Justin Thomas also sent spectators scurrying with his tee shot.

And he's right in the shadow of a tree...

A decent recovery but he's in a bunker I think.

Phil Mickelson is in the thick stuff off the tee on the par-four fifth. No wedge out for Lefty though. He's having a smack at this with a fairway wood. He pushes it into a bunker shy and left of the green.

But when you can play from the sand like that, you can afford to pinball your way down the hole. A four-footer to save par.

Xander Schauffele is walking after his putt almost before he's hit it. He was in the first cut but able to putt and he rattled that in from about 20 feet to move back into a share of the lead.

Can Phil tidy up? Yes he can. We've seen him fight like this countless times before.

American Russell Henley has just grabbed a share of the lead with a birdie on the 15th.

The 32-year-old might be disappointed he didn't come away with more after a lovely approach that left him 3ft from the hole. A birdie is enough to get him to three under alongside Wolff and Koepka, though.

Compatriot Patrick Rodgers is not riding quite so high. He's just carded a bogey one hole ahead to drop out of the lead.

A very wayward tee shot on the 460-yard par four seventh hole from Brooks Koepka, right into members of the crowd sat enjoying a spot of lunch.

Not what he wanted, given things are going his way elsewhere...

Now then, after five straight pars, Matt Fitzpatrick has just claimed back-to-back birdies to move back to two under.

Fellow Englishman Tyrrell Hatton also had five straight pars before seeing a birdie on the 13th cancelled out by a bogey on the 14th. The world number nine is back to one under.