Plans to disrupt the Epsom Derby were foiled as police arrested 31 suspected Animal Rising activists including one who ran on to the track just as the race began.
The man, named by the group as Ben Newman, jumped the fence and sprinted on to the course, dodging a security guard who tried to tackle him.
He was pursued by police as the crowd jeered, with some shouting “get him”, before officers pulled him away and handcuffed him.
Moments later a woman tried to jump the fence in front of the Grandstand as police officers rushed to stop her.
Angry onlookers could be heard screaming, with one man shouting, “kick her head in”, while police threw her to the floor and handcuffed her just as the horses thundered past the finish line.
The ordeal has sparked a row between the Jockey Club, which owns the Epsom Downs, and the activist group, with the latter claiming they breached safety procedures by failing to stop the race when the activist obstructed the track.
Surrey Police confirmed they had arrested 31 people, including 19 on Saturday morning and 12 in the grounds.
Last week, the Jockey Club was granted an injunction prohibiting Animal Rising from intervening in the event, claiming it had made “explicitly clear” it intended to breach security at the Surrey racecourse.
And on Friday, a spokesman for the group pledged to “cancel or severely postpone” the race.
There was disruption at the Grand National at Aintree in April when the race was delayed by just over 10 minutes after demonstrators from the group made their way on to the track.
Speaking after the Derb, the chief executive of the Epsom Jockey Club, Nevin Truesdale, praised the “swift and decisive” action of police in putting an end to the “deplorable and mindless actions” of the protesters.
He described their efforts as “reckless and illegal”, putting the horses and athletes at risk.
“Animal Rising have repeatedly stated that they would not attempt to disrupt any races while in progress and we utterly condemn their deplorable and mindless actions today”, he added.
In a statement on their website after the race, Animal Rising said: “After weeks of speculation and discussion, Animal Rising has disrupted the Epsom Derby.
“After the group hit headlines when it disrupted the Grand National at Aintree, once more it is putting the spotlight on our broken relationship with other animals and nature.”
They quoted Kerri Waters, who they claimed was one of the disrupters, as saying they chose to intervene against horses being used as “objects and property”.
The group also named Ben Newman, who has appeared on GB News, as the man who sprinted on to the racecourse.
In a statement, Surrey Police said: “Eleven people were arrested at addresses in Mitcham and Byfleet in the early hours, following warrants based on intelligence received ahead of the Epsom Derby Festival.
“A further eight people were arrested after their vehicle was stopped on Canons Lane in Burgh Heath at around 10.20am this morning. All were arrested on suspicion of conspiracy to commit public nuisance and remain in police custody.
“A total of 12 people have been arrested within the Epsom Downs racecourse since the event began this morning, also in connection with planned criminal activity.
“One man was arrested after he ran onto the racetrack after a race had started. He was quickly removed by event security and police officers, meaning the race was not disrupted.”
Chief Superintendent Clive Davies added: “Our officers and event security responded quickly and decisively after a man ran onto the racetrack after a race had begun.
“We will not tolerate criminal behaviour which puts lives in danger, including those of the animals, jockeys, security staff and our officers.”