Country House won the 2019 Kentucky Derby after Maximum Security became the first victor in the race’s 145-year history to be disqualified on the day.
The favourite crossed the line first in front of 150,000 fans at Churchill Downs but was ruled to have impeded other horses in the $3m (£2.2m) race.
Maximum Security was disqualified after a stewards’ inquiry lasting 20 minutes.
It left 65-1 outsider Country House, ridden by Flavian Prat for trainer Bill Mott, to be declared the winner.
He is the second biggest-priced winner of the race, which is the first leg of US Flat racing’s Triple Crown.
No horse had ever been disqualified immediately after winning the United States’ biggest race – though Dancer’s Image was stripped of the title in 1968 after a post-race test showed traces of a banned substance.
Maximum Security veered out of line on the final turn and impeded War of Will and Long Range Toddy.
It meant complaints were lodged and stewards reviewed footage and interviewed riders before announcing the disqualification.
As the controversial disqualification was announced, Maximum Security’s rider Luis Saez – who had earlier been celebrating with trainer Jason Servis – put his head into his hands.
“It’s a bittersweet victory but I’ve got to say our horse ran very well and our jockey rode very well,” said 65-year-old trainer Mott after his first Kentucky Derby triumph.
The next step of the Triple Crown is the Preakness Stakes on 18 May, followed by the Belmont Stakes on 8 June.
Only 13 horses in history have won all three races with Justify doing so last year.