Noble Mission led everywhere but the line as Spiritjim foiled his bid for the Group One Grand Prix de Saint-Cloud.
Lady Cecil's stable star has enjoyed a remarkable season thus far and looked set to record back-to-back Group One successes when holding a commanding advantage well inside the final furlong in the historic French contest.
However, his stamina began to painstakingly ebb away in the final few yards of the 12 furlongs and he was nabbed in the very shadow of the post by Pascal Bary's four-year-old who, like the second, was also seeking a four-timer.
Siljan's Saga was a close third
Flintshire had been sent off as favourite following an encouraging return in the Coronation Stakes at Epsom but Andre Fabre's charge was in trouble before the field turned for home with underfoot conditions possibly to blame for his disappointing display.
The winning rider, Christophe Lemaire, told www.paris-turf.com: "I did not panic. I haven't played with the big guys and I rode the race to be second. But when the leader came back to us, I knew that my fighter would give everything."
Pascal Bary has trained some smart performers from Celtic Arms through Six Perfections and Divine Proportions but he was still delighted to claim his 28th Group One and first on French soil since Zambezi Sun won the Grand Prix de Paris in 2007.
"It's incredible," he said. "I really thought we were going to be the second 200 meters from the line. However, 100 meters from the post, my runner has changed his legs and accelerated quickly.
"For once, he didn't have to do the work for others. I must also thank Christophe Soumillon, who has always ridden the horse, but couldn't today. "