Ten years after creating a patriotic storm when winning the Irish Open as a 22-year-old amateur, Lowry has again raised the pride of Ireland, extending his four-shot 54-hole lead to six in extremely demanding final day conditions.
Fleetwood did all he could but other than reducing the deficit to three when Lowry bogeyed his opening hole, the margin was never less than four from the third hole, the quality of play by the winner, especially given the moment, simply sublime.
There had been a potential three-shot swing at the first when Lowry was forced to make made an eight-footer for bogey after Fleetwood missed a makeable birdie putt, a moment that helped settle Lowry according to his later comments and he was more than up to the task over the remaining four hours as rain and wind swept across one of British golf’s finest tests.
A birdie at the 15th after an iron from the tee and a lob wedge to 8 feet sealed any doubt, extending his lead to the eventual margin and he was afforded the luxury of savouring the moment as he embraced, even further, the love and pride of the Irish crowd.
Lowry, of course, comes from the south, the Republic of Ireland, but that appeared to make little difference to the partisan crowd who urged him on as each and every hole passed and the danger of losing the almost unassailable lead faded.
Despite the significance of the win and the fervour of the crowds, Lowry was surprisingly calm in his post-round media conference.
“I'm feeling unbelievably calm, to be honest," he would say. "I don't know why. It's not going to sink in for a couple of days, is it?
“It's just incredible to be sitting here with a trophy in front of me. Look at the names on it. Yeah, I just can't believe - like I said, I couldn't believe that it was me. I couldn't believe it was happening.
"I thought about it all day but I didn't really let myself think about it until I hit my tee shot on 17. As soon as I hit that tee shot I knew that I couldn't really lose a ball from there, and that's how I felt."
The crowd which had been so much with him throughout the week remained through what was an uncomfortable day to spectate and Lowry was aware of their importance in what is his greatest golfing achievement.
“It was amazing. It's hard to believe. It's just hard to believe. I think a lot of people from where I'm from, I spotted a few people in the crowd, and I think a lot of people made the last-minute journey up here this morning because I was leading. And it was just - it was great out there today.
“It's funny, I sometimes struggle to play in front of the home crowd and have done in the past, but not over the last few days. I played lovely. It's obviously very nice.
“It was just incredible to walk down 18. The crowd is going wild. Singing "Olé, Olé." It's like something that - I just couldn't believe it was happening to me. And to have like - it was nice, very nice of Paddy and G-Mac to be standing on the back of the tee for me. And Gary Murphy was there as well, who is a good friend of mine and was great to me when I started out on Tour.
"And obviously to have all my friends and family. I spotted my family when I walked around the corner to have a look where the flag was, and I spotted them all at the back of the green.
“To be honest, I welled up a little bit and Bo told me to catch a hold of myself, I still have to hit a shot. Thankfully I hit a decent shot in there and two-putted.
“To be honest, like, I walked down there and I tried to soak it in as much as I could. It was hard to soak it in because it's very surreal. It's a very surreal experience going down there. Especially with, I'm sure there was a lot of the crowd that wanted me to win today. So it was quite surreal, yeah.”
Twelve months ago, after missing the cut at Carnoustie, Lowry was gutted and winning the Open Championship in 2019 seemed a distant dream a moment he reflected on today.
“Golf is a weird sport and you never know what's around the corner. That's why you need to remind yourself, and you need other people there to remind you. You need to fight through the bad times.
"I sat in the car park in Carnoustie on Thursday, almost a year ago right to this week, and I cried. I didn't - golf wasn't my friend at the time.
“It was something that had become very stressful and it was weighing on me and I just didn't like doing it. And, look, 12 - what a difference a year makes, I suppose.”
Lowry will jump from 33rd to 17th in the world, his highest ever ranking but, more importantly, he won what many will consider one of the best Open Championships on what is, essentially, his doorstep.
He settled a lot of questions not only from the golfing public in general, but even in his own mind, which had at times questioned whether he was up to winning a major championship.
“I suppose I didn't even know going out this morning if I was good enough to win a major. I knew I was able to put a few days together.
“I knew I was able to play the golf course. I just went out there and tried to give my best. And look, I'm here now, a major champion. I can't believe I'm saying it, to be honest.”
Fleetwood was brave himself in the most horrific conditions through the middle of his round.
While disappointed, he was philosophical after his round as to what the day meant and the impact it will have on him moving forward.
“I think first and foremost, whatever happened today was going to be an experience and you were going to take things from it," said the Englishman. "That's the first time I've played in the last group of a major on a Sunday.
“You learn things as you go. You learn things about yourself. I watched Shane in The Open. I watched how he conducted himself and how he played. And for four rounds of golf, I was the second-best player in the event, which is a great achievement. You have to look at it like that. I'm sure in a few hours or a couple of days I might see that.
“But I'll reflect, I think I played a lot of very, very good golf this week. I think for me personally it was nice to play more like I feel like how I should play again. And of course in a major, it's my second runner-up in a major, which is great and I'm trending in the right way. I just hope my time will come eventually.”
Tony Finau finished alone in 3rd place while Brooks Koepka and Lee Westwood tied for 4th.
New Zealand's Ryan Fox came from the cutline on Friday evening to finish 16th after a remarkable weekend and he claimed the spot as the leading Australasian and further cemented his reputation as a fine links golfer.
Cameron Smith finished as the leading Australian in a tie for 20th, fighting hard for so much of his round until three late bogeys cost him dearly. Despite his closing round of 5 over 76, it was the Queenslander’s best finish at the Open Championship.
“You never know what golf can throw at you, I think,” said Smith. “Sometimes you've just got to hang in there even though it's going the wrong way. I actually made a few good bogeys coming in.
“Not that I'm kind of happy but given my results in the past at this tournament, being right up there on the weekend is definitely a good thing.
“I think my game is kind of getting back to where it needs to be."
After a week of relatively low scoring, Royal Portrush reminded everyone what makes links golf so intriguing, not that many needed reminding.
Want video tips delivered straight to your inbox? Subscribe to iseekgolf.com newsletters.