His round gave him a one-shot lead over Italy’s Matteo Manassero, who fired three birdies in the last four holes to complete a fine 67, with five players tied on four under par: Jim Furyk, Brooks Koepka, Sergio Garcia and the two Molinari brothers, Edoardo and Francesco.
Tiger Woods was as impressive as any of those players: after bogeys on the first two holes he produced golf that could have been from his 2006 performance at Hoylake, in which he destroyed the field to win by two shots.
In the afternoon conditions became far tougher as the course dried and the wind picked up a little, raising the scoring average by three shots.
Only two men would trouble the scorers in the afternoon: Adam Scott, world number one and the man who threw away the title two years ago as he imploded on the final four holes, and Ireland's Shane Lowry, a proven winner on links courses, defied the afternoon difficulty.
Scott posted a terrific round of 68 in the worst of it - a performance which was the outstanding showing of any of the late starters - while Lowry took advantage of the breeze easing up later on to make five birdies on a fantastic inward nine which lit up late evening golf.
Scott was happy to keep McIlroy in his sights.
Most of the day's better scores came in the calmer early conditions and Scott was one of the few to make a late run at the 25-year-old Northern Irishman.
"It was tougher this afternoon," he told reporters at Royal Liverpool. "The wind kicked up a bit and the back nine played very tough coming back.
"To keep pace with Rory is important. He has the potential to really put his foot down."
McIlroy's two previous major victories, in the 2011 US Open and 2012 US PGA Championship, were both by runaway margins.
"I've seen him shoot lots of low rounds and there's nothing stopping him from doing that tomorrow either. I don't want him running away...he wins majors by eight shots," added Scott.
The genial Australian is looking to make it third time lucky in golf's oldest major after his agonising second-place finish at Lytham in 2012 and a tie for third spot at Muirfield this time last year.
"This has been a big focus for everyone in my crew this year," said Scott. "We've had our minds on the other majors obviously but to win the Claret Jug is a huge thing."
The 2013 US Masters champion charged to the turn in 31 with an eagle and two birdies before mixing two birdies with two bogeys coming home.
Scott's fellow countryman Bryden Macpherson suffered the embarrassment of plunging to an 18-over 90.
"Tell him to have a couple of beers, that's all he can do," said the world number one.
"I feel for him but he'll bounce back hopefully. We've all had shockers at a major before. I have."
But the morning belonged to McIlroy. The Northern Irishman looked in brilliant touch throughout, firing his opening approach shot to just five feet.
He failed to convert that birdie, and indeed several other makeable chances in a round that might have been even better – yet his near-flawless golf still saw him produce an effortlessly brilliant opening round, with birdies at the 2nd, 5th, 6th, 10th, 12th and 16th holes.
That’s not to say he didn’t make mistakes: twice he got away with poor tee shots, on the 12th and the 17th, bouncing out of thick rough into the fairway on the former, and going so far off line on the latter than he made it past the knee-deep trouble and onto the spectator walkway.
Those two strokes of luck saw him escape with two safe pars – the latter of which came after an excellent five-foot par-saving putt, with his recently-amended, no-nonsense pre-putt routine apparently helping eradicate nerves and the double-guessing which has all-too often characterised McIlroy’s putting on his worse days.
Did this constitute a perfect round, he was asked? "It sort of does, especially in the first round of an Open. I couldn't ask for anymore," he replied.
"I stuck to my gameplan, focused on the par fives and tried to pick up other shots. For the most part my ball was under control and I'm very happy.
"I'm playing well, swinging the club really nicely, holed some nice putts and I'll try to continue to do that and hopefully have another solid round tomorrow. I won't approach it differently."
The challenge now for the world number eight will be his second round: just last week he followed an opening 64 with a second round 78 at the Scottish Open, while at the 2010 Open at St Andrews he fired a second round 80 after tying the all-time low round in a Major with his sublime opening 63.
The weather forecast should help: Friday afternoon, when McIlroy plays again, looks like offering the best conditions of the day. If he keeps things together for a second consecutive day, then a third Major championship victory could be well within his grasp.
- Sports & Recreation
- Adam Scott