In a familiar Ballydoyle versus Godolphin match-up it was the Irish-trained horse who came out on top from the Newmarket hopeful after getting the better of a late duel after dominating the contest from the front end under Ryan Moore.
Desert Castle was sent off the 10/11 favourite under William Buick on the back of two wins from two runs including the Champagne Stakes last time, but he couldn't get past 6/4 chance Darkness Falls who didn't look like relinquishing his advantage deep in the contest, even if the winning distance was only a neck.
Dropping back from nine furlongs, Darkness Falls' stamina was well proven for this seven-furlong task with the question being whether he had the speed to see off Desert Castle.
He proved that in no uncertain terms and this exciting son of Camelot, who O'Brien has already nominated as a potential Triple Crown horse, was cut to 3/1 favourite from 16s for next May's 2000 Guineas by Paddy Power.
Appleby warmly congratulated O'Brien after the race with both trainers happy they have got colts of high potential to unleash in their Classic campaigns next year.
