Royal Ascot winner Sioux Nation got the better of Beckford in a cracking renewal of the Keeneland Phoenix Stakes at the Curragh.
Aidan O'Brien fielded four in his challenge against the previously unbeaten Beckford, trained by Gordon Elliott.
Sioux Nation had won the Norfolk Stakes over five furlongs last time out and was the pick of the O'Brien team by Ryan Moore.
Beckford was sent off the 15-8 favourite but with a furlong to run Sioux Nation's superior mid-race speed enabled him to go a length clear.
To his credit Beckford was reeling him in all the way to the line under Declan McDonogh, but the post came too soon for him, with Sioux Nation (2-1) holding on by half a length to give O'Brien an incredible 16th win in the Group One contest.