Daniel Brown, who won his maiden DP World Tour title in Northern Ireland eleven months ago, took advantage of calmer conditions for the later starters to birdie the third, fifth, 10th, 11th, 16th and 18th for a flawless 65 to move past Shane Lowry and take the opening lead at the 125nd Open Championship.

“I’m very excited but you have to keep your feet on the ground,” said the 29-year-old from Northallerton, who finished 61st in the Scottish Open on Sunday after a run of six missed cuts and a withdrawal in his last seven starts. I am just going to try and go out and do the best I can.”

The contrast between Lowry’s 66 and the 78 of McIlroy immediately brought to mind the 2019 Open at Royal Portrush, when Lowry started with a 67 on his way to the Claret Jug and McIlroy’s chances were blown away with a 79.

“I’m pretty happy, but it’s only one day,” Lowry said. “We’ve got three more days.

“I kept telling myself that out there because for some reason I felt like the crowd were getting very excited. It was late in the afternoon and a few pints of Tennent’s were had out there. It felt more like the weekend.

“I just kept on telling myself there’s a lot more to do so I just kind of stayed in my lane and hit some good shots, and I was pretty happy with how I handled myself.

“The walk down 18 was actually pretty cool. I said to Billy Foster (Matt Fitzpatrick’s caddie) that it’s the greatest walk in golf and I got to do it on a Sunday afternoon with a full house. That’s the plan, to try to get to do that again.

“I’d give anything to win this tournament again. I’d give anything to give myself a chance to win this tournament again and that’s why I’m here this week.

“No matter what I do that week in Portrush will always have a special place in my heart. I love that place and I love this tournament.”

A downbeat McIlroy had earlier dismissed his chances of mounting a challenge for a fifth major title after a costly run around the turn.

Asked if he could make up the ground he had conceded, there was a lengthy pause before McIlroy said: “I mean, all I need to focus on is tomorrow and try to make the cut. That’s all I can focus on.”

Bryson DeChambeau, who edged out McIlroy at Pinehurst to win his second US Open, also found himself well down the field following a 76, although the American did at least hole from 55 feet for an eagle on the 16th.

Thomas had set the early clubhouse target on three under par thanks to birdies on the 17th and 18th, the two-time major winner’s 68 representing a 14-shot improvement on his opening round at Hoylake last year.

“I couldn’t even tell you what I was thinking or how it was then,” Thomas said when asked to compare the two rounds.

“I’m just worried about how I am now, and I’m very pleased with my game and know things are continuing to work in the right direction.”

Former supermarket delivery driver Joe Dean was part of a seven-way tie for fourth place on two under par which included US PGA winner Xander Schauffele and Ryder Cup team-mates Nicolai Hojgaard and Justin Rose.

Rose, who had to come through a 36-hole qualifier to make it to Troon, carded two birdies and 16 pars in a bogey-free 69.

Related: Justin time?

M. James Ward reviews the emergence of the two-time major champion and whether the progress made will be sustained.

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