Starting the 9/10 favourite, he took the lead inside the last quarter mile and accelerated clear of his rivals in the closing stages to win by seven lengths from Elleval.
Starting the 5/2 second favourite, he stayed on strongly in the straight to finish third behind Noble Mission and Al Kazeem, with the unplaced horses including Cirrus des Aigles and Ruler of the World.
Free Eagle was expected to make his 2015 debut in the Tattersalls Gold Cup but was ruled out of the race with what was described as a "head cold".
The race attracted a strong international field including The Grey Gatsby from England, Ectot from France, Spielberg (Tenno Sho) from Japan and Criterion (Queen Elizabeth Stakes) from Australia.
Smullen tracked the leaders before sending the colt into the lead in the straight and held off a strong late challenge from The Grey Gatsby to win by a short head.
[10] Free Eagle was off the course for almost three months before returning for the Irish Champion Stakes at Leopardstown in September and started 100/30 second favourite behind the Epsom Derby winner Golden Horn.
Starting the 16.8/1 fourth choice in the betting he stayed on in the straight despite being slightly hampered and finished sixth, just over four lengths behind the winner Golden Horn.