A 70 today for former world number one Jason Day, now ranked seven and resplendent in salmon pink today. It ends a run of eight scores in the 60s for the Australian but the one under total takes his under-par scores in the Championship to 13 of his last 14 rounds.

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Clubhouse leader Thorbjorn Olesen after his four under 67: "I feel good, I hit my driver well and got myself in some really good positions and it was a really nice way to finish with that long putt on the 18th. I was very excited to get here, the greens have changed a lot with the speed and the grain. It's very challenging but it's good fun to play."

Ken Brown
BBC Sport commentator

The players have been blessed with sun, the course is looking beautiful and there are amazing crowds. It’s all going to plan.

However, perhaps on a day where there hasn’t been much wind you would have expected scoring to have been better, but that is testament to the sheer trickiness of the course. The greens are playing extremely fast and if you get on the wrong side of them, you are going to tipple off.

There have been quite a few birdies made but no rounds where players have escaped without bogeys, particularly on the closing holes - the infamous Green Mile.

That closing stretch is right up there with the hardest finishing three in golf and it has already taken its toll on many players’ rounds today. There is no doubt one of those holes will split the winner from the chasing pack come Sunday.

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Mickelson is in all sorts of trouble on the par five seventh.

He is right, way right, off the tee and that makes a very familiar splashy sound. Yep, the American is going to have to take a drop and is still in a nasty position under some low trees.

He tries to bring the ball back towards the green in the air but it isn't interested and stays wide. Still a fair distance to go.

That's better! A lovely pitch to within 10 feet. Smile Phil. It's not all bad.

After three holes, Rory McIlroy was on the march with a magnificent chip in from just off the green which took him to one under.

Three holes later, and he's one over. There's sure to be a few more twists and turns to come.

Peter Alliss
BBC Sport commentator

They're a little bit concerned by the weather for the weekend, they have a few thunderstorms in this neck of the woods. It's very still at the moment, there's hardly a breath of wind.

That's some impressive scrambling from Byeong Hun An.

From the thick rough he makes par and even had a sniff at a birdie. It tells you how well he's started that he looks a little disappointed with that hole, despite making par.

He's the only player out on the course at the moment really threatening the top of the leaderboard and remains at -3.

Maureen Madill
BBC golf commentator

It is amazing how quickly fortunes can change.

Another one gone for Rory. A duffed chip, one of the worst he has ever hit, and then he charged the par putt five feet past, but in it goes for a bogey, his second of the round. Rahm's birdie effort does everything but drop and he stays level for the Championship.

After an outstanding start of three straight birdies, Byeong Hun An has settled down with back-to-back pars.

Now he's in trouble. That's wayward. Very wayward.

A group of three spectators are forced to take evasive action and the South Korean will have to take his next shot from some thick rough.

The 259-yard par three. I'd be well short with a driver but these lads have lofted irons, McIlroy having jauntily strolled to the tee and delighted fans by touching hands, is pin high in some light rough while Rahm and Fowler have birdie chances from around 20 feet.

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Those of you who are knowledgeable about these things may have spotted the grass on the greens has been changed for this tournament from previous visits to Quail Hollow.

Bermuda grass has been installed in an attempt to improve the putting surface.

My own personal golfing highlight remains a hole in one on the 40-par par three at the Keswick pitch and putt so I'd be the wrong man to tell you the difference that makes but it does produce a picture-perfect course.

It's a hole to forget for Rickie Fowler, a putt of 10 feet slides by and from two under he is back to plus one.

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Maureen Madill
BBC golf commentator

I think the players starting at the 10th have the harder round today because they have the Green Mile stretch with holes 16-18 and then they go to the first, which is the longest opening hole in major championship history so that's a really tough stretch.

More frustration for Phil Mickelson.

The five-time major champ has a little grumble to himself after missing a birdie putt on the fifth. I don't think he can quite understand how that one stayed out. That trademark stomp is back as the leftie mops up and marches on to the next tee.

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Rickie Fowler started well but he is not going to be two under for much longer, his second shot from a fairway bunker at the fifth hit the lip and remained in the trap and his third shot has finished in thick rough.

The highest score of the day so far has come from Australian Stuart Deane, who has returned a 13 over 84, containing nine bogeys and two doubles.

Bernd Wiesberger carded a pretty respectable round of 73 today but he is not amused.

We had mentioned the pace of play here in the office a little earlier and it seems the Austrian has the same issues. For a bit of context it took the Spieth, Koepka, Garcia group around five hours to complete their round today...

Strong emoji use from Bernd too.

Some big numbers around today for the Europeans. Andrew "Beef" Johnston had two double bogeys in a seven over 78 as did fellow Englishman Andy Sullivan, while three-time major winner Padraig Harrington had four double bogeys - three of them in succession - en route to a 79.

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Fowler is the shortest hitter of the group but he's scoring the best so far and he rolls in a second birdie. Rahm sends his four footer for par twice as far away but holes for a bogey and, like McIlroy, is back to level.

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