Rory McIlroy celebrated making a fantastic start to the "fiddliest" Open of his career as his delayed return to St Andrews proved well worth the wait.
America's Cameron Young held the lead thanks to firing eight birdies in a flawless 64, a score only McIlroy himself has beaten in the opening round of an Open Championship on the Old Course.
McIlroy's 63 came back in 2010 and was followed by an 80 in terrible weather, while an ankle injury suffered playing football prevented him from bidding to retain the Claret Jug at the same venue in 2015.
The four-time major winner admitted this week therefore felt like the title defence he never had and he enjoyed an ideal start, holing from 55 feet for birdie on the first and making seven in total in his 66, the same score he shot to begin his wire-to-wire victory at Hoylake.
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In stark contrast, 15-time major winner Tiger Woods had covered his first nine holes in five over, making a double bogey on the first after hitting his approach - from a fairway divot - into the Swilcan Burn short of the green.
Woods, two-time winner around St Andrews in 2000 and 2005, couldn't retrieve the ground, eventually winding up with an opening round of 78, to leave himself with an extremely marginal chance to making the weekend.
An opening 73 in April's Masters meant McIlroy had been a combined 35 over par in the first round of majors since last winning one in the 2014 US PGA, but since then he has started with a 65 in the US PGA, a 67 in the US Open and Thursday's 66.
"Yeah, fantastic start," McIlroy said. "Just what you hope will happen when you're starting off your week. I did everything that you're supposed to do around St Andrews.
"I birdied the holes I should have and I made pars at the holes where you're looking to make a par and move to the next tee, so overall really pleased.
"It's another good start at a major, three in a row for me now, and I'm looking forward to the next few days."
McIlroy is well aware that he has failed to turn those good starts into overdue wins, a third round of 74 doing the damage in the US PGA and a 73 at the same stage of the US Open proving equally costly.
"I need to go out tomorrow and back up what I just did today. I think that's important to do," he said.
"I've been playing well, I've been swinging the club well, and I think it's better if I don't think about it that much and I just go out and play golf and try to shoot some good scores on one of my favourite golf courses in the world."
The parched conditions at St Andrews meant McIlroy was able to reduce the 614-yard 14th hole to a drive - which went around 400 yards - and a wedge, and he added: "It's the fiddliest Open that I've played.
"Carnoustie was firm in 2018 but it wasn't like this. I think as the tournament progresses, you're going to get some funny bounces and it's going to test your patience at times.
"Fiddly hasn't really been my forte over the years, but I'm hopefully going to make it my forte this week."
Two-time champion Padraig Harrington was next-best among the Irish contingent after a fine round of 69 on the thoroughly browned out St Andrews in the evening.
Harrington, conqueror of Carnoustie and Royal Birkdale all those years ago, sits in the pack on -3 in a tie for 13th. Birdies on the 2nd, 9th, 12th and 14th, with a bogey on the 8th left him at -3 approaching the closing holes.
An irksome three-putt from the front of the 16th dented his round but he masterfully escaped trouble at the infamous Road Hole, dinking a perfect chip from the left rough up to a few feet. At 18, he drilled a three-wood to pin high, two-putting from adjacent to the green to card a round of 69.
Shane Lowry, meanwhile, battled back from a nightmarish start to card an even par round of 72, leaving him tied-56th on a day of low-scoring.
Lowry was rocked by an early double-bogey on the 2nd after firing his drive into a gorse bush down the right-hand side and he fell back to +3 following a bogey on the 4th.
However, birdies on the 5th, 9th and 10th saw him clamber back to even par. A disappointing bogey on 13 was swiftly followed by a birdie on 14.
"I got off to the worst possible start and fought back well," the 2019 champion said afterwards. "After a bad tee shot on the second I didn't really do much wrong after that. I'm pretty happy with how I'm playing.
"I'm not down in the dumps by any means about my day. It's not the end of the world. It's not middle of the field. It's better than middle of the field."
Seamus Power, starting early, is a stroke further back on one-over par, birdies on 1, 9, 10 and 18 being cancelled out by three bogeys and a double-bogey on the par-4 12th.
The late-starting Irish pair of David Carey and Ronan Mullarney finished in declining light, the latter holing out for a par as part of the final group at 10.25pm.
Castleknock's Carey birdied the final hole to card a composed even par round of 72, his four bogeys being cancelled out by birdies at 1, 5, 9 and 18.
Galway man Mullarney reached the turn in 33, his outward nine decorated by an eagle at the par-5 5th hole. However, four bogeys on the back nine saw him fall back to +1 following a creditable 73.
2011 champion Darren Clarke carded a seven-over par round of 79.
Leader Young had missed the cut in his last two starts, but the world number 32 has recorded four top-three finishes on the PGA Tour this season and missed out on a play-off for the US PGA Championship by a single shot.
And the 25-year-old revealed this was not his first experience of playing the Old Course thanks to a family trip 12 years ago.
"I think my dad asked for permission to play from the back tees so when we came out to hit our first tee shots with the R&A building right there, there were a bunch of R&A members presumably watching," Young said.
"And I'm glad I didn't know, I'm sure I would have been nervous out of my mind. But I think there's a picture of me hitting there with a bunch of those guys watching. That's really my first memory of here."
Scottie Scheffler made a typically low key but efficient start to his title bid with a solid four-under-par 68,
The American world number one, who won this year's Masters and finished tied second in the U.S. Open, collected five birdies and a single bogey around the Old Course to finish in the group four shots behind Young.
On a day when the early starters took full advantage of benign conditions, Australia's Cameron Smith carded a 67 while amateur Barclay Brown returned a superb 68 which was matched by Viktor Hovland and Lee Westwood.
Westwood's fellow LIV Golf rebel Ian Poulter had been booed by a handful of spectators on the first tee due to his involvement in the Saudi-backed breakaway, but turned the jeers to cheers after holing from 150 feet for an eagle on the ninth in his 69.
There was disappointment for his Ryder Cup team-mate Justin Rose as he was forced to pull out with a back injury just before his scheduled 8.14am tee time, with Japan's Rikuya Hoshino taking his place.
Sweden's Alex Noren had been first reserve but he chose to travel to the Barracuda Championship in California.
Additional reporting: PA/Reuters
