Maximum Security has led all the way in the Kentucky Derby only to become the first winner disqualified for interference in the race’s 145-year history.

After a long wait, long shot Country House was declared the winner

Country House, a 65-1 chance, finished second in the sloppy conditions on Saturday (Sunday AEST) before an objection was raised, causing a lengthy delay while stewards repeatedly reviewed several angles of video footage, before he was elevated to first.

The stunning outcome gave Hall of Fame trainer Bill Mott his first Derby victory at age 65. Jockey Flavien Prat, who originated the objection, also won his first Derby.

Country House paid $132.40 to win – the second-highest payout in Derby history.

It was a crushing turn of events for trainer Jason Servis and jockey Luis Saez, who already had begun celebrating what they thought were their first Derby victories.

Instead, Maximum Security was demoted to 17th of the 19 horses. The colt was the 9-2 second choice in the market.

Prat claimed Maximum Security ducked out in the final turn and forced several horses to steady.

War Of Will came perilously close to clipping heels with Maximum Security, which could have caused a chain-reaction accident.

The stewards reviewed race footage for nearly 20 minutes while keeping the crowd of 150,729 in suspense.

Code of Honor was moved up to second and Tacitus was third.

Credit: AAP