Dream Eater landed the first prize of £191,533 with an emphatic victory in the Samsung St Leger 2-Y-0 Stakes.
Doncaster racecourse has undergone a £32m overhaul
Andrew Balding's grey lined up with 21 rivals at the newly-redeveloped track, opened by HRH The Princess Royal on the first day of the St Leger meeting.
Dream Eater (15-2) led just inside the final furlong on the far side and quickly went clear for Franny Norton.
Achilles of Troy (10-1) was length and a quarter back in second and Copywriter (16-1) a head away in third.
Balding said: "That's a nice way to break your maiden and his work has been improving at home.
"I was a bit worried when I saw him sweating in the parade ring but he can do that - Franny gave him a great ride."