Oh no! Rory McIlroy is in deep trouble here as he finds some long, high fescue off the tee on the fourth, and can only bunt it forwards a few yards.

From there though he ends up on the side of a hump just by a bunker, and then another fluffed effort follows befre he finally excapes and finds a fairway with his four shots, and still miles away from the green on this 621-yard hole.

It's a par five but he'll be hitting his fifth from 178 yards away....

An excellent second into the 11th, his ball grabbing the green and pulling up eight feet from the hole gives Bob MacIntyre a really good birdie look.

But a yelp of frustration speaks volumes as his ball misses the hole. You don't get many chances like that round Oakmont, and the Scot knows it.

An outside chance of a birdie on the fifth is just missed by JJ Spaun but he cards another par to continue his bogey-free opening round at Oakmont.

Goodness me - one of the strangest bogeys you'll ever see from Bryson DeChambeau!

The defending champion is over the back of the 12th green in two, then he chips off the right side of the green coming back and lands in more long grass.

Two more attempts later, he is still on the fringe of the green. So he gets out the putter and sinks a very tricky putt from 25 feet for an eventful six.

Xander Schauffele also bogeys the par five and is now three over.

Ludvig Aberg makes a nice par five on the long fourth - playing 621 yards today - after having to hack out of the rough with his second.

Adam Scott plays the hole brilliantly to cover those 621 yards and leave just a five footer for a birdie, but he misses! A huge chance goes begging and the former Masters champion stays at one under.

Image source, Getty Images

Gary Woodland, the US Open champion of six years ago, is progressing along without too much alarm in a tie for second place.

Another par on 11 keeps him at three under and, like leader JJ Spaun, he is yet to card a bogey in his round today.

Take a bow Shane Lowry! He's been beaten up good style by Oakmont today, but responds magnificently on the third as he only goes and holes out from 160 yards for an eagle!

Lowry has been trudging along, shoulders, hunched, looking a battered and broken man after that double bogey on the last, but that's a massive shot in the arm and even though he looks a bit embarrassed that could be a big momentum shift for him.

Thomas Detry closes out his front nine with a third birdie of the day to turn in three under and in a tie for second. Superb stuff from the Belgian so far.

Propping up the leaderboard at this early stage is Justin B Hicks, a 50-year-old from Florida.

He's the oldest qualifier and is +11 after 12 holes. No huge disasters for Justin, just seven bogeys and two doubles.

Hicks is making his seventh appearance at the US Open - his first was in 2004 at Shinnecock - and first since he made the cut in 2016, right here at Oakmont.

Rory McIlroy actually has half a chance at the second with 16 feet for birdie, but it's just a par in the end - which he'd probably have taken from where he was in the rough.

Shane Lowry would bite your hand off for a par here as he makes his second double bogey of the day and he's now tumbling down the leaderboard at six over.

Yes he can!

JJ Spaun is putting a heck of a first round together at Oakmont.

He stays one shot clear of the field after sinking an eight-footer for par.

Work to do for JJ Spaun on the fourth after that wayward tee shot.

He's in the greenside bunker in three - can he get up and down to save par?

Stephen Watson
BBC Sport Northern Ireland at Oakmont

It may be the brutal rough at Oakmont that grabs the headlines but the greens are just as evil.

Former Ryder Cup captain Paul McGinley, now an analyst with Golf Channel, said he’s never seen faster or more sloping, treacherous greens - not even at Augusta National, the venue for the Masters.

In preparation for this major, Oakmont has made the putting surfaces even larger and more formidable than before.

Rory McIlroy is short of the second green but in the rough, so he chops it out and tries to run it up this huge slope (another one!) on this putting surface.

The ball just about gets there but just runs out of juice and threatens to tumble back down off the green, so McIlroy gets on his toes and runs up there to mark it while it's still.

Veteran move.

Bryson DeChambeau left himself a 16-footer for birdie on the 11th but couldn't make, so another par it is for the defending champion.

Xander Schauffele matches his fellow American to remain at two over.

Bob MacIntyre has a look of frustration on his face as he watches his birdie putt from just off the front of the ninth green steam a good seven feet past the hole.

A par saver here and he'll head to the 10th in buoyant mood. But he doesn't get the read and shoves his putt to the right of the hole and that saunters a good three... four feet beyond. The bogey putt drops.

Image source, Getty Images

Video clips have flooded social media in the past few days showing just how challenging Oakmont promises to be for this US Open.

The United States Golf Association has confirmed that the rough will be "uniformed at five inches" across the golf course, while the greens are set to be among the fastest the players have experienced, registering at almost 15 on the stimpmeter.

With the world's best players struggling to locate their balls in the manicured jungles, lining the fairways and greens, AKA, the rough, what hope would say an 18 handicapper have around these parts?

Justin Rose reckons 140, Justin Thomas went with a range of 110-120, Jason Day reckons 150, while Tommy Fleetwood left his prediction at "it'd be a lot".

What do you think, folks?

Ludvig Aberg gets back to two under with a birdie at the third - where he again makes the most of finding a fairway.

Adam Scott though drops a shot here to add a fourth bogey of the day to his card to go along with his five birdies in an eventful opening round for the Australian.

Image source, Getty Images

Between the third and the fourth fairways at Oakmont, the Church Pews bunker is one of the most famous and intimidating sights in golf.

Measuring 110 yards long and 42 yards wide, this famous bunker features 13 pews that are all three-feet tall and it apparently holds 550,000 tonnes of sand.

Leader JJ Spaun's tee shot on the fourth has just landed on one of those pews...

Stephen Watson
BBC Sport Northern Ireland at Oakmont

At Oakmont, one of the big sellers at the US Open merchandise stands is a cute, fluffy squirrel.

It was introduced as the club’s iconic logo in 1962.