GRAND National protesters broke through the ring of steel and stormed the track at Aintree before 118 people were arrested.
Activists delayed the races this afternoon by 15 minutes after running onto the racecourse and gluing themselves to fences.
Cops swooped in after the group managed to get into the grounds just minutes before the horses were due to leave their paddocks.
At around 5pm people were seen leaning ladders up against barriers before accessing the grounds - with up to 100 protesters trying to breach security.
As police and event officials tackled activists, many were led away in handcuffs.
More people claiming to be part of animal rights groups have since blocked the M57.
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Merseyside Police confirmed protesters wearing pink t-shirts were sat at junction 2 heading northbound.
All 118 people arrested have been taken into custody on suspicion of criminal damage and public nuisance offences in relation to disruption at the Grand National, Merseyside Police Assistant Chief Constable Paul White said.
Chief Const White added: "The safety and wellbeing of everyone is of paramount concern when dealing with a large-scale public events such as the Grand National.
“The perimeter of Aintree racecourse covers an extensive area of between 4-5km and obviously poses challenges for policing.
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"However we have been planning the policing of this event for a number of months and we had a robust plan in place to ensure that we had adequate staff to deal with it.
“Just after 5pm a large number of protesters attempted to gain entry onto Aintree racecourse.
"The majority were prevented from breaching the boundary fencing thanks to our planning and the work of my officers.
“I can confirm a total of 118 people have been arrested today.
“I would like to thank everyone for their patience whilst this matter was dealt with in a safe and appropriate manner.
"I would also like to take the opportunity to thank mutual aid officers from Greater Manchester Police, North Wales Police, Cheshire Police and Durham Police and our partners at Aintree racecourse, security providers and the Jockey Club for their assistance in dealing with this matter.”
Footage showed brave locals helping police contain the protesters on the track at Aintree.
Organiser Peter Scudamore said: "It's just part of what we have to go through.
"I'm sorry for the horses, the protesters doing this, well it affects the welfare of the horses."
An Aintree Racecourse spokesperson added: "We respect the right to peaceful protest but sincerely hope that Animal Rising reflect on whether their proposed actions are legitimate and responsible.
"Their actions could endanger the horses they purport to protect, as well as jockeys, officials and themselves.
"As you would expect, we are working closely with Merseyside Police to ensure we protect the safety and enjoyment of everyone, including all participants, human or equine, at the Grand National."
Christine Maybin, 29, from Antrim, Northern Ireland, said: "We noticed the delay but we didn't know it was because of protesters, we thought they were fixing the fences.
"We only noticed the protesters when we were coming in from the train."
Dwayne McGurk, 31, said: "The delay didn't affect us, we just got another drink in. We've had an unbelievable day here."
It comes after animal rights groups, who object to using horses for entertainment and sport, previously revealed their intentions to disrupt the famous Aintree event.
Three people were taken into custody this morning over a plot to protest the racing event.
Police confirmed the trio were arrested on suspicion of conspiracy to cause public nuisance.
A woman, 25, was taken into custody around 11.10am and the man around 30 minutes later.
A 33-year-old woman from the London area was also taken in by cops.
A spokesperson for the force this morning said: "Merseyside Police has been working with The Jockey Club and other partners to keep people safe during the Grand National Festival.
“We are aware of some people planning to protest at the event. This has been factored into our plans.
"We respect the right to peaceful protest and expression of views, but criminal behaviour and disorder will not be tolerated and will be dealt with robustly."
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Earlier in the day, police nabbed suspected ringleader Rose Patterson, 33, Claudia Penna Rojas, 25, from London, and a 55-year-old man from Greater Manchester on suspicion of conspiracy to cause public nuisance following a 30-strong protest outside the gates of the Merseyside course.
The force have now thanked the public for their patience while they dealt with the issues.