Back down the third fairway and our leader is about to fall down the leaderboard.

Im Sung-jae, with his slow, deliberate backswing, tugs his drive into the church pew bunker down the left. His ball lands in the sand and is up close to one of the grassy pews. And he's made a bit of a horlicks of that, only advancing the ball into thick rough (is there any other kind of rough of Oakmont?!)

His stance is awkward and he bunts a low runner up the fairway towards the green but that's pulling up a good 60 feet short of the flag. And that's for a par...

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A first birdie of the day for Jon Rahm, on the third, his 12th of the round. It's a straightforward three-footer to cancel out a solitary bogey.

Sam Burns is back into the top five as he cashes in on the par-five 12th.

It's an outstanding chip out of the rough with his third shot to land inches from the hole. He's up to two under for his round.

Been nice to see consistency from Brooks Koepka today who has not threatened major championship leaderboards since winning the US PGA in 2023.

He's in sand trouble down the 13th but whisks out a neat wedge to six feet and tidies up successfully.

There's a roar from behind that green too as Justin Thomas sinks a long birdie putt to nudge back to five over par.

That's the first birdie for this entire group.

We have a new leader. Im Sung-jae is on the second green in two and staring down an eight-footer for a fifth birdie of the day.

He dribbles the ball down the hill and it tumbles into the hole.

No signs of Viktor Hovland disembarking the birdie train. That's three on the spin and all three have followed sensational approach shots.

Scottie Scheffler also does the business from 20 feet. Will that provide the spark over his remaining seven holes.

Brooks Koepka has to settle for a par on the 12th to stay at one under, while Min Woo Lee makes a par five.

Justin Thomas in more trouble thanks to a visit to the fairway bunker and his US Open looks to be almost over already as he slips back further to six over.

And incredibly that means that we've not had one single birdie from this group today - with just Koepka's eagle the only hole played in under par by this threesome all day!

More evidence that you don't want to be going in the rough too often at Oakmont.

Jordan Spieth pitches from the long grass straight into a greenside bunker but battles to make par and stays at one under.

Jon Rahm only just clears the same sand trap but his ball rolls down the slope of the green, further and further away from the hole.

The Spaniard saves par though, to continue one of those rounds where not a lot has really happened for him - but actually that's not a bad thing, given how tough this course is playing. Slow and steady is just fine - one over par won't be a bad score at all today.

Scottie Scheffler hasn't quite found his range with his irons yet. His approach into the 11th is good but again that touch of back spin means it ends up 20 feet from the pin instead of the 12 feet Collin Morikawa will be putting from for a birdie.

Viktor Hovland is throwing darts at present as he lands his ball in to three feet. Could this be a third straight birdie for the world number 14.

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Wonderful stuff from Im Sung-jae - he's into a share of the lead!

A lengthy birdie putt on the first - his 10th hole today - takes him to four under par.

Like Spaun earlier, the man from South Korea has not dropped a shot so far today.

Speaking of Patrick Reed and his albatross a little earlier - it was the first at any major championship since Nick Watney's in the 2012 US Open in the first round (Hole 17 at the Olympic Club).

The other only other two in US Open history were from TC Chen (1985 at Oakland Hills, round 1, hole 2), and Shaun Micheel (2010 at Pebble Beach, round four, hole six).

Patrick Reed ends his front nine with a bogey to drop back to one under, but that's more than a decent score for their front nine at Oakmont.

Of course, it'll be tinged with disappointment having hit that incredible albatross but still - he's well in the ball game here.

An epic par for Brooks Koepka on 11 as he produces a perfect escape from the bunker, where you could barely see the top of his cap peaking out above the deep sand trap.

He clips the ball off the sand though and lands it softly on the correct side of the hole to use the slope to roll it down, almost in, but a gimme for par.

Par, bogey, birdie, par, birdie, bogey, birdie....Matt Wallace is on some run of holes.

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Jordan Spieth has looked the most likely of this trio to mount a challenge to JJ Spaun's lead. His fourth birdie of the day, set up by a sensational approach to the first green, takes him back under par for the championship.

Jon Rahm reads his long birdie putt from the front of the green very well to earn an eighth consecutive par.

But Dustin Johnson posts another bogey. He went way right off the tee and played off a pathway back into play, but couldn't get up and down in two from the back of the green.

Collin Morikawa plays a laser-guided second shot into two feet on the 10th and without tempting fate it's hard to see this not resulting in a birdie. Yep a formality.

It is followed by another gem of a shot from Viktor Hovland, to maybe three feet at most and he is able to tidy up for his birdie.

Scottie Scheffler's ball spins back though and he will be the odd man out with a par.

We've said it before, but it's a funny old game isn't it? Patrick Reed holed out from 286 yards earlier today, and now he's just stubbed a chip from the left of the ninth green that's gone maybe four feet in front of him.

That's golf!

Incredible scenes on the 11th as both Min Woo Lee and Brooks Koepka hit decent drives away but just fail to get to the top of the huge hill that is the fairway, so their balls stop and roll back down the hill towards them and into the first cut.

Lee manages to find the green nicely enough from 180, but from nine yards closer Koepka makes a big error and tugs his approach into the left greenside bunker - with not too much green to work with either.

That's a tough up and down from there.

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Defending US Open champion Bryson DeChambeau conceded Oakmont was a difficult challenge on day one:

"This golf course can come up and get you pretty quick and you've just got to be on your game, and it got me, and I wasn't fully on my game.

"I think the rough is incredibly penalising. Even for a guy like me, I can't get out of it some of the times, depending on the lie.

"Pretty disappointed with how I played. It's not too far off. Just got to get the putting a little bit more dialled, and I'll be right there.

"It was tough - a brutal test of golf - but one that I'm excited for tomorrow. If I just tidy up a couple of things and get some momentum going my way, we'll see where it goes."

Scottie Scheffler is going right through it on the ninth. His up and down from around 90 yards to save par, goes horribly wrong as his pitch spins back from pin high and trundles off the green.

The American is two over after the front nine along with Viktor Hovland, whose sparkling iron shot to a foot leaves a gimme putt for birdie.

Collin Morikawa also surrenders a shot following his troubles in the sand. Oakmont is looking as hard as it has ever been at present.