Well, they said a filly might win it — but very few had in mind the one whose success here yesterday was received by many as some kind of chimera conjured from the befuddling heat.
The mirage that was Danedream gained unequivocally in substance, however, from every detail of her rout. She won by five lengths and broke the track record.
Prior to the immaculate Zarkava, in 2008, the Prix de l'Arc de Triomphe had last been won by a filly in 1993 — and Urban Sea was so prepotent an animal that she has since given us Sea The Stars and Galileo.
Moreover, you have to go all the way back to 1975, to Star Appeal, for the last German winner.
While fillies duly filled the podium, as some had anticipated, the identity of the runner-up was more outlandish still.
Shareta had been treated as a mere pacemaker for Sarafina but was ridden with circumspection after Treasure Beach hurtled into a clear early lead, and so held on for second.
Of the females who had seemed so much deadlier beforehand, only Snow Fairy enhanced her reputation in third, closing well after the winner had flown.
Best of the colts was So You Think, who was left with plenty to do after being dropped in by Seamus Heffernan from his difficult draw.
St Nicholas Abbey kept on steadily for a fine fifth, after briefly asserting in the straight, with Meandre and the favourite Sarafina closing upsides from midfield.
Galikova was nearly brought down on the inside as the field tightened and there will be other days for her, but the Japanese never got involved and Workforce ran poorly. Reliable Man, whose connections had likewise been concerned about firm ground, beat only Masked Marvel home.
It had been another blazing day in the Bois de Boulogne, with the Sunday joggers staggering in sweaty disbelief along the dusty paths and very little blush as yet in the trees.
Though the track had been heavily watered, the turf baked through the afternoon and conditions doubtless contributed to Danedream's molten time.
But there was less trouble in behind than had seemed likely, Galikova apart, and nobody could be deceived that there was the remotest fluke about what transpired.
Danedream had been improving so rapidly, winning a Group One prize by six lengths on her previous start on home soil, that her connections had paid €100,000 to supplement her to the field on Thursday.
There had admittedly been doubt whether Danedream would be comfortable with conditions.
But settled behind the leaders by Andrasch Starke, Danedream moved up powerfully in the straight and as she broke clear it was at once apparent that she would not be caught by the field.
The significance of her achievement was not lost on those who hopped and sobbed around their filly. Only Ribot, Sea-Bird and Sakhee had dominated an Arc more.
Starke was still roaring even after he had dismounted.
“I don't know what has happened,” he said.
“It's a dream come true — it was a dream for me just to ride in this race.”
Danedream is stabled with one of Germany's most accomplished horsemen in Peter Schiergen.
“This is a really big day for German racing,” the trainer said.
“And my best moment in racing. I don't believe it.
“She won her last two races very easily, but I didn't think she would be such an easy winner.
“She is a small filly with a big, big heart.”
He indicated that Danedream will remain in training and so not be seen again this year.