Group One form came to the fore in the Ambant Gala Stakes at Sandown as Mandour wore down Afsare inside the final furlong.
Alain de Royer-Dupre's French raider had finished third in the Prix d'Ispahan behind Maxios last time out and quickened up stylishly under Christophe Lemaire.
Luca Cumani's Afsare had looked like claiming the spoils for much of the straight as James Doyle's mount moved to the head of affairs on the bridle, but he could not hold off the 9-4 favourite who ultimately won cosily by three-quarters of a length.
John Gosden will be thrilled by the comeback run of Excess Knowledge who made late headway to claim third, just ahead of Mike de Kock's David Livingston with Guineas third Van Der Neer only fifth.
"He was third in a Group One and we wanted to find an easier race for him, although it wasn't so easy," Royer-Dupre said.
"He needs time to show his turn of foot and he always runs like that.
"He has an option of a Group Two at York (York Stakes) or maybe something in Deauville. He's very immature and it was important for him to learn to travel."