World number one Brooks Koepka cruised into contention for a fifth major title in his last 10 starts as Rory McIlroy's hopes of ending his five-year drought were effectively ended by two nightmare holes in the 148th Open.
At the venue where he announced himself as a star of the future with a course record of 61 aged 16, McIlroy began with an eight and finished with a seven in a demoralising opening 79 at Royal Portrush.
At eight over par McIlroy was 12 shots off the clubhouse target set by Ireland's Shane Lowry, whose 67 gave him a one-shot lead over a nine-strong group which included Koepka, Sergio Garcia, Scotland's Robert MacIntyre and the English duo of Tyrrell Hatton and Tommy Fleetwood.
Koepka finished second in the Masters in April, successfully defended his US PGA title the following month and was runner-up to Gary Woodland in the US Open in June.
No player in the modern era has placed in the top two in all four majors in a calendar year, but the 29-year-old made the most of the local knowledge of his caddie Ricky Elliott, who hails from Portrush, as he carded four birdies and one bogey in his 68.
New Zealand's Ryan Fox was alongside Koepka on three under after firing six birdies in the last seven holes to card the first back nine of 29 in Open history.
"I'm just trying to get out of my own way at the minute and enjoy being out there and that finally worked today," Fox said.
"I've missed seven cuts in a row and to figure it out in a major is certainly nice. It's the first round in a while where I had some fun and some control over the golf ball."
An understandably nervous McIlroy could certainly not say the same as he ran up a quadruple-bogey on the first after pulling his tee shot out of bounds on the 424-yard par four.
McIlroy's wayward iron shot hit a female spectator and damaged a mobile phone in her pocket before ending up five feet outside the white posts which mark the internal out of bounds.
The four-time major winner then found the left rough with his second attempt and hacked his fourth shot into a bush from where he took a penalty drop, chipped to seven feet and two-putted for a demoralising eight.
Another shot went at the third before McIlroy picked up his first birdie of the day on the par-five seventh and narrowly missed for another on the next, those two holes being created from the adjacent Valley Links to replace the original 17th and 18th which are being used to house the spectator village.
A birdie from 15 feet on the ninth took McIlroy to the turn in three over par but after six straight pars he three-putted from five feet to double bogey the 16th and then ran up a triple-bogey seven on the 18th to complete a miserable day.
"I'd be disappointed regardless, whether it was here or St Andrews or Birkdale or any of the other tournaments or majors," McIlroy said. "So, yeah, I'm disappointed, but at the end of the day I'm still the same person.
"I'm going to go back and see my family, see my friends, and hopefully they don't think any less of me after a performance like that today. And I'll dust myself off and come back out tomorrow and try to do better."
Lowry's 67 was his best opening round in any major and he said: "It's my best by about eight shots. That was nice. It was nice to shoot a good score and hopefully I can go out and keep at it the next few days."
