A woman was also detained by officers after being pulled to the floor when she tried to invade the course.

It comes after 19 people - believed to be animal rights protesters - were arrested on Saturday morning over plans to disrupt the event.

A total of 12 people were detained within Epsom Downs racecourse during the event on Saturday, also in connection with planned criminal activity, Surrey Police said.

Sky's Becky Cotterill, who was at the Surrey course, said: "I could see there was a guy that appeared to run on to the track and was quickly removed by security guards.

"The race had started at that point, but they seemed to get him off the track without causing any disruption to the race, so the horses carried on."

Louise Hilwood, a spokeswoman for Animal Rising, told Sky News: "Someone did make it on to the track today and that's a huge success - not only because they got on the track, but because we managed to start this national conversation about what happens, not only to racehorses, but to animals throughout many industries, including our food system."

The group had warned it would attempt to sabotage the event, despite a High Court injunction.

Surrey Police said 11 people were arrested at addresses in Mitcham and Byfleet in the early hours of Saturday, while eight were arrested around 10.20am after a vehicle was stopped in Burgh Heath, just south of Epsom.

All were arrested on suspicion of conspiracy to commit public nuisance and remain in police custody.

Dan Kidby, co-founder of Animal Rising, said the police operation ahead of the event was intended "to protect the interests of a multi-billion pound industry" and that "a horse dies every other day in racing".

The group also accused police of "heavy-handedness" and "overreach", referencing updates to the Public Order Act which give officers new powers to crack down on some protests.

Surrey Police Superintendent Michael Hodder said: "We have been clear in our approach that criminal activity will not be tolerated at the Epsom Derby Festival.

"As a result of intelligence, we have arrested 19 people who we believe were intent on illegally disrupting today's events.

"Our officers will be at the event throughout the day to continue in keeping the public safe and preventing criminality."

Surrey Police had said it would not tolerate any risk to public safety and that anyone involved could be subject to contempt of court proceedings, fined or jailed.

An injunction sought by The Jockey Club during the week banned people from going on the racecourse and carrying out acts with intent to disrupt the races.

Nevin Truesdale, Chief Executive of The Jockey Club, said: "Our security teams and the police acted swiftly and decisively to remove an Animal Rising protester who entered the racetrack after The Derby had started and while the race was being run.

"This reckless and illegal behaviour which threatened the safety of our equine and human athletes is a breach of the High Court injunction which The Jockey Club obtained last week and prohibits trespass. The court order provides a clear route to prosecution, fines and even the threat of prison for Contempt of Court and we will now take steps to enforce that.

"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.

"The Derby was first run in 1780 and has continued despite two world wars, the COVID pandemic and a number of other extreme challenges. That the 244th running of the race was able to take place on time today is testament to the determination of everyone to stage one of British sport's most iconic and loved events."

There was disruption in April when protesters managed to delay the start of the Grand National by around 10 minutes after they managed to get on the track.