The Queen's horse Dartmouth is the new favourite for the King George VI And Queen Elizabeth Stakes at Ascot following the withdrawal of Postponed.
Trainer Roger Varian said the former odds-on favourite was found to have a respiratory infection after failing to work as well as usual.
Victory for Dartmouth on Saturday would give the reigning monarch her first win in the race named after her parents for 62 years, with Aureole claiming it in 1954.
Cox Plate third placegetter Highland Reel from the Aidan O'Brien stable is seen as Dartmouth's main challenger.
Dartmouth is at 15-8 with Highland Reel at 2-1.