Home favourite Rory McIlroy suffered a nightmare start, including an opening-hole quadruple bogey, while Ireland’s Shane Lowry took the clubhouse lead.

Organisers the R&A are anticipating the second-biggest ever Open attendance, with 237,750 people expected to come through the gates this week in Northern Ireland, but spectators were left stunned by McIlroy’s immediate collapse.

He briefly battled back after a bogey at the par-three third hole, but missed a tiny putt to double-bogey the 16th, tripled-bogeyed the last and eventually carded a disastrous eight-over 79.

“I guess when you play your first and last holes in a combined seven over par you are starting on the back foot,” said McIlroy.

“The first hole was the first hole, it was a rough start but I felt like I showed some good resilience after that and played the next 12 or 13 holes in two under par and then really what I’m disappointed about is I undid all that good work in the last few holes.” The 30-year-old is already 12 strokes adrift of clubhouse leader Lowry, who rolled in five birdies in a fine four-under-par round of 67.

World number 33 Lowry admitted he also struggled to keep his nerves in check on the first tee, with the crowds lending strong support to all six players from the Republic of Ireland and Northern Ireland.

“I felt uncomfortable on the first tee, I was glad it was downwind so it was only a three iron,” he said.

“It’s the British Open, it’s in Ireland. I feel like I’m hitting it well. Of course I feel uneasy.”

The 32-year-old Lowry is one shot clear of six players who signed for three-under 68s -- Swede Alex Noren, former US Open champion Webb Simpson, South African Dylan Frittelli, Sergio Garcia, Scotland’s Robert MacIntyre and Thai Kiradech Aphibarnrat.

Four-time major champion McIlroy, who fired a course-record 61 at Portrush at the age of just 16 in 2005, was given a huge reception on the first tee as the crowds huddled around the opening hole for a sight of the local hero.

However, cheers soon turned to stunned silence and then groans as McIlroy hooked his opening iron shot out of bounds, hitting a watching fan and reportedly breaking her mobile phone in the process.

The world number three then pulled his second shot from the tee into the rough, he had to take a drop after finding an unplayable line next to the green and two-putted to post an eight on the par-four first.

Reigning champion Francesco Molinari saw his hopes of becoming the first man to defend the title since Padraig Harrington in 2008 take a blow, only managing a three-over 74.

“That was not the first round I was looking for,” said Molinari. “I’ll try to learn from today and do better tomorrow.”

The later starters were also making moves, with world number one Brooks Koepka ominously making his way to two-under through 10 holes and England’s Tommy Fleetwood reaching the same score after 11.

Tiger Woods began his bid for a 16th major title at 1410 GMT and parred his first three holes, with heavy showers forecasted to continue into the afternoon.

Argentina’s Emiliano Grillo got the crowds excited with the first hole-in-one at the championship since 2016 on the par-three 13th.

There were cheers elsewhere on the Dunluce links early on as another Northern Irishman Darren Clarke, who hit the opening shot of the tournament, started brightly before hitting two bogeys in the final three holes for an even-par round of 71.

Tiger Woods made a horrible start to his bid for a 16th major title at the British Open on Thursday, slipping to six-over par after only 10 holes of his opening round.

Struggling off the tee, the 43-year-old American, followed by swathes of spectators, started with four straight pars before his game fell apart dramatically at Portrush.

Woods made four bogeys and a double bogey at the par-three sixth.

His troubles followed those of the other crowd favourite, Northern Irishman Rory McIlroy, who quadruple-bogeyed the first hole en route to an eight-over 79.

Woods found himself 11 shots behind early pace-setter Jon Rahm, who raced to five-under after only nine holes, and 10 adrift of clubhouse leader Shane Lowry.

Agencies