Dustin Johnson headlined the Friday morning charge at The 150th Open.
The American backed up his four-under-par opening round with five-under-par 67 as he climbed to the top of the leaderboard on nine-under ahead of the overnight leaders teeing off.
Johnson had produced one of the better rounds in difficult conditions on Thursday afternoon and carried that momentum over to his early start on Friday to put himself right in the mix.
A bogey on the 1st proved to be only a momentary setback as birdies on the 3rd, 9th, 10th, 14th, 16th and 18th holes saw him overhaul compatriot Cameron Young at the summit.
He has previous at St Andrews, leading after the first and second rounds the last time The Open was played on the Old Course in 2015, shooting 65 and 69 on that occasion.
While he ultimately fell away over the weekend seven years ago to finish T49, Johnson has four top 10s at golf’s original Championship and looks primed to challenge once again.
When asked about whether he could learn anything from 2015, Johnson said: “No, just keep doing the same thing. I feel like I have got a good game plan.
“Kind of depends on the wind direction, how you attack the golf course. I feel like I am swinging well. Obviously, it is just avoiding the bunkers as much as possible.
“It is really hard not to hit it in one of the bunkers. I have been in three so far, and two of them I had to chip out sideways, and the other one I had a shot.
“If I can just keep out of the bunkers and just keep playing kind of smart golf where, when I have a good number and a club that I can get it close to the hole, I can be aggressive.
“But when not, just kind of hit it to 30, 40 feet and try to two-putt. To be honest, I do not even remember the third round from seven years ago. I have played a lot of golf since then.”
The former world number 1 was far from the only man on the move on Friday morning, though, with fellow American Talor Gooch shooting a three-under 69 to get to seven-under-par.
Bogeying the 16th was the only blot on another very impressive round, which included two birdies on the front nine and two on the back, a result Gooch was more than happy with.
“My only bogey of the day was a three-putt on the 16th. So I was able to keep the ball in the fairway. I avoided the bunkers today and the pins were really, really good,” he said.
“They were really challenging. It was tough to get it close. The times that I was hitting it 60, 70 feet out, I was able to two-putt those all but once. Did a good job of bogey avoidance today.”
When asked about playing the home of golf, he added: “There’s nothing better. It's the mecca of golf. The crowds, the volunteers, just the support of this whole community, it is super special.”
Adam Scott, playing with Johnson, also vaulted himself up the leaderboard with the best of the morning scores, finishing with a sensational bogey-free 65 to move to seven-under-par.
He had been three-over-par through six holes of his first round before recovering to finish level par and Scott insisted that fightback paved the way for his Friday morning momentum.
“That is what I needed. Look, as good as the 65 was today, I think getting back to even was huge yesterday. After six holes things were not feeling particularly good,” he said.
“So I am really pleased with that. I did a lot of good stuff out there today. So hopefully more of that on the weekend. I was pretty solid today. I think my striking was solid enough.”
Scott memorably finished second at The Open in 2012 after letting a four-shot lead slip in the final four holes, handing the Claret Jug to Ernie Els at Royal Lytham & St Annes.
That collapse still weighs heavily on the 41-year-old’s mind, with Scott admitting he still has designs on getting both hands on the Claret Jug after coming so agonisingly close to victory.
“You do not need much extra motivation at an Open Championship,” he added.
“But anytime I think about letting one slip through my hands, it hurts. It would be exciting if I shot a really great round tomorrow to tee off with a legitimate feeling that I'm in contention.
“Not only for the fact that I have not really been in that position for a major for a little while, but also for the fact that I have had one hand on this jug, I feel like, and I would like to put two on.”
Sergio Garcia is another player who has experienced Open heartbreak before, finishing second to Padraig Harrington and Rory McIlroy in 2007 and 2014, respectively.
A six-under-par 66 on Friday, which included an eagle on the 9th, saw the Spaniard rise up the leaderboard as he responded in style to his three-over-par 75 on Thursday.
The birdies also flowed freely for world number 1 Scottie Scheffler and Tyrrell Hatton, who recorded rounds of 68 and 66 to join the party on eight-under-par.
But it was undoubtedly Johnson who stole the show on Friday morning and while he played down his 2015 disappointment, he could not hide his desire to lift the Claret Jug.
“It is a big tournament. It is a great tournament,” he said.
“Obviously if you look at the history of it, it is a golf tournament that I would love to have. It is a trophy I would love to have in the office when I am done with my golf career.”