Two years after starting the Open Championship with a quadruple-bogey eight, Rory McIlroy began his first round at Royal St George's with a birdie three.

And although the four-time major winner was unable to build on that ideal start, McIlroy was happy to battle back from a hat-trick of bogeys on the front nine to card a level-par 70.

"It probably doesn’t make a huge difference at one over or even this early in the tournament, but mentally it feels a bit better to birdie the last and I’m looking forward to getting back out tomorrow," McIlroy said.

"Tommy (Fleetwood) shot a great 67 which is probably the best of our wave in the afternoon. Benjamin Hebert shot 66 but was out a touch earlier than us.

"When we were warming up it felt like a nice breeze but when we got out there, especially out by the water, it was really windy. Anything around even par today was pretty good.

"After that little wobble on the front nine I set myself a little target of getting back to even par and I was able to achieve that and that feels good. I’ll probably sleep a bit better tonight and feel a bit better going into the second round."

Asked about the difference between his opening hole at Royal Portrush in 2019 and today, McIlroy added: "No out of bounds on this first hole, it’s nice.

"One of the things I struggled with the last couple of weeks was the driver and to hit a tee shot like that down the first, 350 (yards) or whatever down the middle and then stuff a wedge close was the perfect start.

"I drove the ball way better than I have the last couple of weeks."

Jordan Spieth remains unconvinced that a curious coincidence means he has a 50/50 chance of winning the 149th Open Championship, although his prospects look bright following a superb start at Royal St George's.

South Africa’s Branden Grace has played alongside the eventual winner in the first two rounds in both 2018 and 2019, with Spieth and Bryson DeChambeau getting the prized draw this year.

And although DeChambeau complained that his driver "sucks" after an opening 71, Spieth had no cause for concern following an opening 65 to lie a shot off the lead held by fellow former Open champion Louis Oosthuizen.

"I think that’s a coincidence," Spieth said with a smile when asked about the 'Grace effect’. "If it happens four or five times in a row, maybe people start paying to see who can get paired with him the first two rounds.

"I think that when you have a top-50, top-25 player in the world that Branden has been, he’s going to be in some pairings with guys who are certainly capable of winning major championships and it just so happened it was two years in a row.

"I did hear that ahead of time, though, which just made me laugh."

Spieth, who claimed his first victory since winning the 2017 Open at Royal Birkdale in his native Texas in April, bogeyed the third but bounced back with four straight birdies from the fifth and also picked up shots on the 15th and 16th.

The former world number one fell to 92nd in the world rankings following a missed cut in his first event of the season, but the 27-year-old has since recorded six top 10s in strokeplay events, including a tie for third in the Masters.

"I look back and I had a chance to win at least one of the majors each year when I felt like I had no idea where the ball was going which, I guess, could be bad and good," the three-time major winner said.

"Golf is a game played between the ears, right? When it’s not going great, you can certainly lose quite a bit of confidence in it. That was the first time I’ve had to really try and build confidence back up, and it takes time.

"By no means do I feel like I’m where I want to be mechanically yet, but this year has been a really, really good progression for me, and all I’m trying to do is just get a little bit better each day."

Louis Oosthuizen

Oosthuizen carded a flawless six-under-par 64 to enjoy a one-shot lead over Spieth and Brian Harman.

Already a runner-up in all four major championships, Oosthuizen took his unwanted total of near misses to six by finishing second in both the US PGA Championship at Kiawah Island and the US Open at Torrey Pines this season.

Asked how he copes with such losses, the 38-year-old South African said: "It depends if you lost it or someone else beat you. In both of those I was beaten by better golf at the end.

"It takes a little while but you have to get over it quickly otherwise it’s going to hold you back from performing again."

Oosthuizen currently leads the putting statistics on the PGA Tour and is so pleased with that part of his game that his old putters could even be consigned to a watery grave.

"I’ve got a bag there at home that I might just throw in a river someday," Oosthuizen joked.

"I found one that I really like the look of and I worked on it. There were tournaments where I felt my stroke wasn’t great and I would actually change that putter then for the round. I didn’t want to have any bad memories of that putter being not good on the day."

Two months removed from becoming the oldest major champion in golf history, Phil Mickelson's Thursday at the Open Championship was far more forgettable.

Mickelson shot 80 in his first round at Royal St. George's in Sandwich, England, and at 10-under was tied for last in the field of 156 golfers. According to the Golf Channel broadcast, it was Mickelson's worst career round at the Open in 27 starts.