There were moments he stumbled on the path and fumbled for his keys. But as he marched down the 18th fairway, as the crowd rose to their feet and their shouts and cheers rang out, the doors swung open and McIlroy was welcomed in. Now it's official. Now he is one of the greats.
A lot of players have bolted out of anonymity, picked up a major, then bolted straight back again. A few - say, Andy North and Retief Goosen - were top players of their times, but were slightly flattered to get two of the most cherished titles in golf. Nobody ever got three by luck. Once you've got a hat-trick you're rubbing shoulders with giants.
Last night, McIlroy stood on a pedestal as the first citizen of Europe to have won three different majors. If he can triumph at Augusta next year, or in any other year for that matter, he will become the first European to complete a career grand slam, joining Gene Sarazen, Ben Hogan, Jack Nicklaus, Gary Player and Tiger Woods.
It is worth considering these things. Already, he has done something that neither Nick Faldo nor Seve Ballesteros could pull off. At the age of 25 he is firmly in the frame for consideration as the best golfer these islands has ever produced. He enriched his father Gerry yesterday by delivering on the wager that he would win the Open before the age of 26, but he has enriched the sport as a whole.
And he has charmed it. Tiger Woods in his pomp would often give the impression of being a corporate entity - branded, buffed and shorn of every vestige of character. That facade collapsed in the scandals that engulfed him a few years ago, but McIlroy is protected by the fact he has never built a wall of artifice around himself. He is a long way short of Woods' achievements as a golfer, but he is streets ahead as an engaging human being.
At 25, McIlroy is past the point of being described as playful, but he goes about his business with wonderful good humour. When he collected the Claret Jug last night, he impishly thanked the Liverpool crowd for getting behind a Manchester United fan. They responded in the same spirit, with some pantomime booing. And then the applause rang out again.
McIlroy even coped superbly with the brain-dead spectator who appeared to think it funny to goad and heckle him. Eventually - when the idiot coughed on his backswing at the 16th - McIlroy pointed out the offender to army marshals, and the individual was removed. "He was giving me grief all day," McIlroy reported. "I sort of put up with it for the first 15 holes."
For 15 holes? The fellow would not have got past the first tee had he been following Woods. There is a lightness about McIlroy that makes him one of the most appealing figures in sport. And there is a wonderful humility with it.
The first thing he did after his winning putt was embrace his mother Rosie, standing behind the 18th green. "My mum wasn't at my previous two major wins," he said. "It was just my dad. It was great to see her at the back of the 18th and see how much it meant to her. I was trying not to cry at the time because she was bawling her eyes out. The support of my parents has been incredible. Growing up and doing everything, the sacrifices they made for me. Even today, they are the two people in this world who I can talk about anything with. I couldn't ask to have two better parents."
Nor they a better son. There was an impression a couple of years ago that McIlroy was becoming a little too fond of the trappings of success - for goodness sake, who in his position would not succumb to a few temptations - but in a number of ways he has returned to his roots, appearing more grounded than ever. His loyalty to friends is legendary. A couple of weeks before his trip to the Open he joined a number of them on a lads' break in Ibiza. When he walked into the scorers' area at Hoylake last night, a group of them were there to welcome him.
No doubt he will take the trophy back to the County Down village of Holywood and they will hail him as rapturously as they did at Hoylake. "Just to be sitting here looking at this trophy and having my name on it is a great feeling," he smiled. "I'm going to enjoy it and let it sink in in the company of friends and family.
"I'm immensely proud of myself. To be here at 25 years of age and win my third major and be three-quarters of the way to the career grand slam, I never dreamed of being at this point so quickly.
"The Open Championship was the one you really wanted, the one you imagined yourself holing putts to win, to beat Tiger Woods, Sergio Garcia, Ernie Els, whoever. I didn't quite need to hole a putt to do it, just a little tap-in, which was nice."
He talks freely of wanting to be the sport's most dominant figure. If anyone else said the same thing, they would rightly be accused of arrogance and would carry a burden of hubris. McIlroy, however, will carry the hopes of many as he continues his quest. Hopes and expectations. The golfing gods welcomed McIlroy in last night, but there is much more to come from this remarkable young man.