His gait, on days like this, is unmistakable, even from a par-5 away. When Rory McIlroy is playing his best golf — and his best golf is about the best golf on the planet right now — he carries himself as the best golfer in the world. His chest is out, his head upright, his gaze forward and the ground beneath his feet seems to bounce him upward. He is in command of everything around him, and he wants every single person who glances his way to know it.

So here he was Friday evening, walking up the 18th fairway at Royal Liverpool Golf Club for the completion of the second round of the British Open, swagger fully engaged. When the grandstands thundered at his arrival, he gave a casual wave of acknowledgment with his left hand. Thanks, it seemed to say. I know well what I’ve done and what I can do.

“I don’t know if I can describe it,” McIlroy said. “I feel . . . just like I have an inner peace on the golf course.”

Play like McIlroy has the past two days — back-to-back 66s to get to 12 under par and a four-shot lead over Dustin Johnson — and peace would seem easy to come by. When, exactly, did he hit a wayward shot? Maybe at the first Friday, when he blew his approach through the green, leading to his only bogey in 36 holes.

But pick apart the other 131 strokes and find a flaw. Over these two days, McIlroy has earned the right to walk like he owns the place because, for the moment, he does. The 25-year-old Northern Irishman has won two majors — the 2011 U.S. Open at Congressional Country Club and the 2012 PGA Championship at Kiawah. Each time, he taught the field how the game is played, winning by eight. He knows how to administer a whuppin’.

Dustin Johnson of the U.S. sits all alone in second place at 8-under-par after a second-round 65 on Friday, the low round of the afternoon. (Cathal Mcnaughton/Reuters)

“I’m very comfortable in this position,” McIlroy said. “I’m very comfortable doing what I’m doing right now. . . . I think it’s a combination of confidence, just being mentally strong, mentally aware of everything.”

So bring on the comparisons to McIlroy’s lap of the field at Congressional. They are inevitable. The Blue Course, normally with so much teeth, had every last fang removed that moist June week, much as Royal Liverpool has been susceptible for much of the field this week, what with the wind largely under control. In Bethesda, McIlroy led by three after the first round, six at the midway point, eight after the third and eight to win.

Here, his opening 66 gave him a one-shot lead over Matteo Manassero. On Friday, his 66 appeared just as dominant because he responded to that opening bogey with steadiness — until he went for the throat. His two-putt birdie at the par-5 fifth was built on the back of a titanic drive; he hit pitching wedge for his second shot on a 528-yard hole. He then struck an 8-iron to seven feet at the par-3 sixth, and at that point, just before 4 p.m., the crowd roared its approval because McIlroy had a two-shot lead. The strut carried him to the seventh tee.

“I thought, ‘This feels good,’ ” McIlroy said.

He does not have the lead he had at Congressional only because Johnson, the mammoth hitter who tied for second at the 2011 British Open, actually had the best round of the tournament, a bogey-free 65 that he closed with two birdies to get two clear of six players at 6 under. But when the third round begins Saturday morning, Johnson will be playing with someone who could, at the moment, be his equal with the driver.

“When his driver is on, he’s almost unstoppable,” said Rickie Fowler, who first encountered McIlroy when the two were amateurs at the 2007 Walker Cup. “He’s a very good driver of the ball when he is on. . . . I don’t think he has a whole lot of weaknesses. I know there’s been a couple Fridays where he’s struggled a little bit and kind of fallen back.”

Ah, yes, the Fridays. If there has been an issue that has nagged McIlroy, it is this. His scoring average in the second round ranks 181st on the PGA Tour this year, and he has faced questions about it at every turn. They intensified after Thursday’s 66, with the British press dubbing them “Freaky Fridays.”

Rory McIlroy pauses on the 8th green to allow a pheasant to putt out — er, vacate the putting surface — Friday. (Scott Heppell/Associated Press)

“Hopefully,” he said, “I put it to bed today.”

There is one potential obstacle for McIlroy — and the field. The forecast for Saturday is so bad — thunderstorms beginning overnight, dissipating in the afternoon but returning later — that the R&A decided it would send players off both the first and 10th tees for the first time in 143 British Opens.

“Anything can happen,” said Graeme McDowell, McIlroy’s countryman.

The bet, though, might be that McIlroy reduces anything to the inevitable.

“You run out of superlatives when you’re describing the kid’s game,” McDowell said. “He’s unbelievable, and no one will be surprised if he addresses the third leg of the Grand Slam this weekend.”

When McIlroy stood over his final five-foot birdie putt at the last, a siren blared in the background from the nearby neighborhood, just beyond the massive grandstands. A single ambulance couldn’t rescue the entire field, right? McIlroy rolled in the putt, gently pumped his right fist, shook hands with his competitors — and then strode off the green, unmistakably and completely in charge.