The Elie Lellouche-trained Westerner beat off a strong British and Irish challenge to land the Prix Royal-Oak at Longchamp this afternoon.
Ireland's top stayer Vinnie Roe was sent off favourite as he tried to repeat his 2001 success in the race and turning for home Dermot Weld's triple Irish St Leger hero held every chance.
But down the straight the Pat Smullen-ridden five-year-old weakened as Hughie Morrison's veteran Alcazar emerged from the pack as the bigger danger.
Michael Fenton's mount finished strongly up the centre of the track, but crossed the line two and a half lengths adrift of Westerner.
The Aga Khan's Behkara took third, a length further back, with Vinnie Roe the same margin away as he faded into fourth.
Weld's Ivowen took third in the Listed Prix Casimir Delamarre behind Criquette Head-Maarek's Salydora.