Un De Sceaux just held the late thrust of Gemix to take the Grade Three Prix Hypothese at Auteuil in Paris.
Barry Geraghty, replacing the injured Ruby Walsh, set out to make all on the Willie Mullins-trained Irish raider and the tactics were rewarded - albeit by a narrow margin.
At one point Un De Sceaux was at least 15 lengths clear but his lead began to diminish in the straight as the unbeaten six-year-old was stepping up to two miles, three and a half furlongs.
Gemix put in a strong late bid from the last two flights and just failed to peg back Un De Sceaux. Monpilou was best of the rest in third, but never nearer.
Un De Sceaux got the verdict by a short neck, much to the delight of connections.
"His best form may well be at two miles, but we took a chance and it paid off" - Patrick Mullins
"Obviously we were going over there and taking on the French champion hurdler [Gemix] in his own backyard," said Mullins's son, Patrick.
"I imagine we'll probably bring him back in trip but he showed a bit of battle to hold on.
"His best form may well be at two miles, but we took a chance and it paid off - he jumped [fantastically] as well.
"He's in at Punchestown. We'll see how he comes out of this. He has had a hard enough race.
"Today was the plan and he's won. It's great prize-money over there and the owner has had a great day out in Paris.
"The horse has maintained his unbeaten record so it's success all round."