THE oft-used cliche about a round of golf completed in some comfort is that it is a walk in the park.

This description fitted most of Rory McIlroy's journey around Royal Lytham & St Annes yesterday. Then his afternoon turned into something resembling a park scene in darkest Lanarkshire.

There was a crash, a roar, some blood and a body down. The US Open champion of 2011 had smacked his drive at the 15th off the head of somebody standing by the swings. Sorry, somebody standing by a hamburger van. The ball took a Lanarkshire stoat off the victim's head and spiralled 20 yards into what is called out of bounds, specifically in this case not-so-darkest Lancashire. "He could have headed it the other way," said McIlroy, bravely overcoming his remorse and dreaming of a ball bouncing back on to a fairway.

If the incident was bruising, McIlroy repaired the immediate damage by offering the stunned chap a golf glove with the word "sorry" sporting a sad face. If professional golfers commandeered air traffic control and subsequently sent a jet crashing to earth, they would make up for by signing in tribute a golf glove and, perhaps, a ball.

They have their minds on other concerns. McIlroy's priority was to salvage a decent round after a double bogey and he did this almost routinely by driving the par-4 16th and claiming a birdie and then by narrowly avoiding trouble at the 18th and draining a good putt for another gain on par. He thus finished on three under after a round that was blissfully serene except for the surreal moment on the 15th.

The most impressive aspect of the Northern Irishman's performance was that it was strangely unimpressive. This is not to suggest that it was crude or lucky or a struggle. Rather, it was smooth, calm and matter of fact. The 23-year-old shot 67 in the Open Championship without a strain, almost without a care and while drawing a sad face.

McIlroy, accused of being distracted by his romance with tennis player Caroline Wozniacki and dismissed by many as a threat at this year's Open because of a perceived inability to play in rain, placed himself carefully near the top of the leaderboard and his play suggested, almost in a whisper, that this was just the beginning. "I was under control most of the day," said McIlroy, putting a smiley face on the 15th. "From tee to green, I was very, very calm. My emotions were good. Everything was feeling pretty good."

The incident at the 15th was unfortunate for the spectator – who immediately but woozily said he was okay – but it was unlucky, too, for McIlroy as the ball bounced out of bounds by a matter of inches. The reaction from the world No.2 was a mark of his growing maturity. He admitted that in the past he may have "fizzled out" and "let it get to me". Instead, he said: "'I liked how I reacted. I did well to keep my composure and keep my concentration."

The contrasts in what was a walk in a park was philosophically written off as a case of "swings and roundabouts".

More tellingly, McIlroy seems quietly enthused about the course. "It's a very fair test," he said. "On a golf course like this, the cream will rise to the top. I think you are seeing that with the leaderboard today."

Another Northern Irishman who is also a US Open champion is also at three under. Graeme McDowell confidently negotiated the course with undue alarm and rightly is prepared to challenge over the next three days. "I like the way this course is set up," said McDowell, whose control off the tee restricted him to two bogeys, one inevitably at 15.

He was also helped by putting more than efficiently and making intelligent decisions on how to play the testing holes. "Every shot is a conundrum," he said. "You have to get in a relaxed frame of mind," said McDowell of a day when he and his compatriot made the most of benign conditions. "You have to get your attitude correct and accept that you will make mistakes. I did that well today. I reacted well to my mistakes. That's all you can ask for."

This request was made by another Northern Irishman but was denied. Darren Clarke, the defending champion, will not have to create room in his car for the Claret Jug this year after a 76. "It's a long drive back home," he said, anticipating an early release from his duties. "I'm disgusted with myself for shooting six over. I've got to go and practice. I have to work."

The 43-year-old was a popular, if unexpected winner at Sandwich but has had a low-key season with his rounds averaging more than 73. His frustration was obvious and it was made worse by what he believed was his failure to merit the loud applause he received as he walked the course yesterday. "I tried to stay patient," he said. "I tried my best. It just didn't happen."

He added: "I do think you could publish my thoughts right now." Clarke could recall only one "lovely" shot and that was his tee shot at the first.

The rest was an exercise in how golf can make a walk in the park a forced march. Just what was Clarke's abiding memory of his day as defending champion? "Probably coming up the last thinking how the bleep did I manage to win this last year."