Vow And Declare repelled Irish and British challengers to win the Melbourne Cup for Australian trainer Danny O’Brien in a dramatic finish.
The winner, ridden by Craig Williams, denied jockey Frankie Dettori on Master Of Reality, with Prince Of Arran third.
But stewards are looking at potential interference by Dettori, who rode the runner-up for Irishman Joseph O’Brien.
His mount drifted across fourth-placed Il Paradiso, trained by Joseph’s father Aidan, in the closing stages.
Dettori, 48, looked to have sealed his first victory in the two-mile race ‘that stops a nation’ but Williams edged past to claim his maiden Melbourne Cup triumph.
“It was a privilege to ride him today and great to be associated with such a great horse,” said Williams.
The winning trainer said: “It’s an amazing win, a special thing to happen.
“I really can’t believe it, I just feel incredibly blessed to have a horse good enough to be in it. The last 100 (metres) he just wouldn’t give in.
Prince Of Arran, for British trainer Charlie Fellowes, finished third for the second year running.