This victory, the rider’s first in the race, brought up a hat-trick of Group One wins for the rider aboard Coolmore-owned horses during the afternoon.
And even Fallon, who has experienced every kind of high and low in the racing game in recent seasons, admitted it was probably the best day of his racing career.
Well in rear in the early stages, Fallon seized upon a gap which opened up on the inside of the field as the runners hit the home straight.
Suddenly, having looked to have it all to do, Hurricane Run was surging up the rail, picking off his rivals one by one.
The good news for racing fans is the son of Montjeu - who himself won this race in 1999 for Hurricane Run’s part-owner Michael Tabor - will stay in training next season.
And there must be every possibility given his late-maturing profile the colt will go on to even better as a four-year-old.
Tabor also refused to totally rule out a trip to the Breeders’ Cup later this month for the winner, who certainly did not seem to have that hard a race, even in the muddy conditions.
The two pacemakers, Windya and Voltmeter, had done their jobs well by setting a decent gallop in the rain.
Frankie Dettori was the first to commit on Cherry Mix, but Godolphin’s hope could not maintain his challenge, while Shawanda - who was ridden close to the pace - was another in the firing line with two furlongs to run.
Next to hit the front was Derby hero Motivator, cheered on by the Royal Ascot Racing Club legions, who found an opening on the inside and briefly stuck his head in front a furlong and a half out.
But it was soon Westerner who looked the likeliest winner, the brilliant stayer having been slightly outpaced off the hme turn but now flying down the centre of the course with a full head of steam.
However, with each change in the running order at the head of affairs, Hurricane Run was steadily gaining ground and he led inside the final furlong to beat Westerner by two lengths.
Last year’s Arc winner Bago flew late to grab third, with Shirocco fourth and Motivator losing two places in the final strides as he faded into fifth.
It was a riding performance of audacity and brilliance, Fallon following his earlier wins on Rumplestiltskin in the Prix Marcel Boussac and the Prix Jean-Luc Lagardere on Horatio Nelson.
But Fallon is no more or less a maestro of his profession than Hurricane Run’s trainer Andre Fabre, who was winning the race for the sixth time having struck with Sagamix (1998), Peintre Celebre (1997), Carnegie (1994), Subotica (1992) and Trempolino (1987).
“When there is a strong pace you can afford to ride them like that,” Fallon said as he reflected upon the race. “I could have made my move sooner, but I knew they were going quick enough and when they do that they often fan out across the course and leave gaps open.
“I made the right decision. You take risks going up the inside but if often pays off when you go that way. Eight times out of 10 it’s the right thing to do.
“I had a lot of confidence in him today. He was on his toes but he felt really good going to post.
“He is growing up all the time. When I rode him at the Curragh he was a big baby but he’s going the right way now.
“It’s been a great day and it doesn’t get any better than three Group Ones - although having said that it was nearly four as Mona Lisa was a bit unlucky when she finished second!”
Having finished second in the French Derby, his only defeat, Hurricane Run was purchased by Tabor to join the Coolmore stallion team at the end of his racing days.
But having seen son emulate father, the owner looked more amazed than anyone as he watched replays of the race in the winner’s enclosure.
“Somebody asked earlier if you can still get excited when this sort of thing happens, but to see that race ought to answer that for you,” Tabor said.
“I still cannot believe he managed to win from where he was. He just showed what a good horse he is. It was something to behold.
“I don’t know about the Breeders’ Cup for him. We haven’t discussed it at all so I guess we need to sit down and talk it through.
“But he will definitely stay in training next year. We want to enjoy him - that’s what racing is all about.”
Westerner is also set to remain in training next season after turing in the performance of his life to finish second.
Admittedly suited by the ground and the early gallop, the six-year-old showed tremendous courage to comfortably prove far stronger than all of his rivals bar one.
And trainer Elie Lellouche said he would be happy to campaign the horse at a mile and a half again in the future, opening up a number of opportunities.
Owner Alex Wildenstein added: “I was delighted with that. I am very proud of the horse. The only thing is perhaps he was a little too close and free early on, but he has run very well.
“Olivier (Peslier) gave him a very good ride and I have no doubt we took the right decision running him here. I would much rather finish second in the Arc than win the Cadran.”
Hong Kong rather than Melbourne is the likeliest next stopping point for Westerner.
Third-home Bago heads for the Breeders’ Cup Turf in search of his consolation, but the participation of Motivator in that race may now be in some doubt with connections considering Newmarket’s Champion Stakes as an alternative.
“He did very well, but it’s all about winning in this game,” said trainer Michael Bell. “It’s very unfortunate the gap opened on the rail a bit sooner than we would have wanted. He hit the front with 300 metres to run which on this ground, into a head wind, is quite a tall order.
“I have to say, maybe the winner would have beaten us anyway so we have still run a very creditable race, but you really need everything to fall into place in these races.
“I think that next time we will play our hand a little later, but I don’t think Johnny (Murtagh) had a choice but to take the gap that opened for him today when he did. It was just one of those things.
“There is the Breeders’ Cup for him, or the Champion as an alternative.”
Motivator and Bago are both available at 8-1 with Coral for Belmont, with Azamour remaining the 4-1 favourite.
Aidan O’Brien tightened his grip on the betting for the Classics with a Group One double thanks to Horatio Nelson and Rumplestiltskin at Longchamp.
Kieren Fallon went straight into the lead on Horatio Nelson in the Prix Jean-Luc Lagardere and he always looked to have matters well under control.
After seeing off the challenge of Sylvester Kirk’s Opera Cape, the son of Danehill drew readily clear to score in good style by one and a half lengths from the British challenger.
Horatio Nelson was cut two points to 10-1 by William Hill for the Derby, but remains a 10-1 shot for the 2000 Guineas. Totesport go 8-1 for Epsom and 6-1 from 8-1 for the Rowley Mile Classic, while Paddy Power go 8-1 for both races. Coral have cut the colt’s odds to 7-1 from 10-1 for the 2000 Guineas and quote him at 8-1 for the blue riband.
O’Brien said: “We haven’t ruled out the Breeders’ Cup. He is a staying horse, but he has also got plenty of speed.
“You only need to look at his times to see that he is quick and I don’t think a mile of the Guineas would be too sharp for him.”
Kirk said of Opera Cape: “We’ve been beaten by a very good horse. That was my first Group One runner and I can’t complain with coming second.
“We’ll start him off next season in the Greenham and see what happens.”
Rumplestiltskin cemented her position at the head of the betting for the 1000 Guineas with a narrow but convincing victory in the Prix Marcel Boussac.
She came from an unpromising position under Fallon from her wide draw to lead well inside the final furlong and get the better of Quiet Royal and the Clive Brittain-trained Deveron by one length and one and a half.
Coral were most impressed and cut her odds for the Newmarket Classic next spring to 3-1 from 7-1, with Ladbrokes longest at 5-1.
“Kieren gave her a masterful ride,” O’Brien said. “It looked like she wasn’t going to get any room, but he said he always hoped it would drop right for him.
“She stays a mile well and she is a possible for the Breeders’ Cup (Juvenile Fillies’).”
Fallon added: “She didn’t have the best of draws and there was always the possibility that we would find trouble in running. The gaps opened when I needed them to and she has done it well.
“She’s a very good filly with a very big future.”
Brittain was delighted with Deveron’s effort and said: “Kerrin (McEvoy) said if he hadn’t been hampered they would have finished much closer.
“She will be trained for the UAE Guineas.”
There was a turn-up in the Prix de l’Opera when rank outsider Kinnaird emerged victorious to provide Middleham trainer Patrick Haslam with his first Group One success.
The consistent but luckless filly had not won since the May Hill Stakes in 2003 and put the record straight under a determined ride from Kevin Darley.
She led well over a furlong out and held on gamely when strongly pressed by O’Brien’s runner Mona Lisa and hot favourite Alexander Goldrun.
The post arrived in time and she prevailed by a head and three-quarters of a length.
Haslam was also on the mark at Kelso with Kerry’s Blade and he was represented by his wife Anne.
After after greeting the 69-1 shot on the pari-mutuel, she said: “It’s easy to say so now but Patrick really felt that he had her at her best today.
“She’s been very unlucky for the past couple of seasons with a couple of little injuries, but we’d had a clear run coming in today’s race, she was as fit as she could be and all we needed was soft ground and a bit of luck.
“She really deserved this. We’ve been waiting for this sort of ground for so long.
“She may go to Canada now for the E P Taylor Stakes and could possibly stay there to be covered by a very good stallion.”
O’Brien said Mona Lisa would now head to Belmont Park for the Breeders’ Cup Filly & Mare Turf.
Despite her defeat Alexander Goldrun remains on course for the Hong Kong International Cup at Sha Tin in December, a race she won last year.
Her trainer Jim Bolger said: “She broke well, she had a good passage, she just never picked up. We reckon it was just an off day.
“Hong Kong will be next on the agenda.
“The plan has always been for her to stay in training next year, but I suppose we’ll have to see.”
Alcazar ran his usual good race when he dead-heated for second place in the Prix du Cadran.
Hughie Morrison’s evergreen 10-year-old was unsuited by the steady early pace and was caught flat-footed when the tempo increased.
But to his credit he stuck on well, albeit too late to trouble Reefscape. He got up on the line to share second with Ostankino, two lengths adrift of the winner.
His jockey, Michael Fenton, said: “They went a bit steady for me.”
Morrison put a brave face on defeat and added: “You can’t win when you are that far off the pace.
“It looked quite a winnable Cadran this year, but we’ve come second in a Group One and you can’t complain too much.
“Provided he stays sound he’ll be back in training next year.”
Reefscape was scoring at his first attempt at the marathon trip of two and a half miles and he will be prepared for a tilt at the Gold Cup next year.
“A more genuine horse you couldn’t dream for - he goes on any ground,” said his trainer Andre Fabre.
“He will stay in training next year and will be back for the Gold Cup at Royal Ascot.
“We’ll have to see if he stays in a truly-run race but why not have a go?”
The victory was owner Khalid Abdullah’s first in the Group One stamina test.