Odds-on favourite True Story was third as The Grey Gatsby (9-1) won the Dante Stakes at York.
Jockey Ryan Moore guided the Kevin Ryan-trained winner home from runner-up Arod, surviving a stewards' inquiry over possible interference in the race.
True Story is now 16-1 in places for the Derby at Epsom on 7 June, having previously been second favourite.
Australia, trained in Ireland by Aidan O'Brien, is now odds-on market leader for the Classic at about 4-6.
The Grey Gatsby was 10th in the 2,000 Guineas on 3 May, in which Australia finished third to winner Night Of Thunder.
Ryan's Mastercraftsman colt does not hold an Epsom entry and is more likely to be aimed at the shorter French Derby.
"That (extended mile and a quarter at York) is as far as he wants to go," said jockey Moore.