Celestial Halo turned in a magnificent display to win the Gras Savoye Corporate Life Prix La Barka.
The nine-year-old, trained by Paul Nicholls and owned by Andy Stewart, shaped best in the torrential rainfall to claim his first victory since January 2012.
Last season's World Hurdle runner-up was a close-up second as Lord Prestige led after the last, but Daryl Jacob's mount (10-1) showed characteristic bravery to get up at the line.
Thousand Stars, who won this Grade Two 12 months ago, appeared very unhappy early on but stayed on to take fourth spot, with Tidara Angel in third.
Willie Mullins dominated the Gras Savoye Pasteurdon Prix Questarabad when Blood Cotil outgunned Diakali in the Grade Two over hurdles.
The latter was always to the fore under Ruby Walsh, but was let down by a wayward leap at the last.
This helped the Paul Townend-ridden Blood Cotil seize the day along the run-in at odds of 8-1.
Le Grand Luce (7-4 favourite) was third, with fellow Mullins inmate Viconte Du Noyer taking fifth spot.