The race started at 5.27pm (instead of 5.15pm) after around 15 Animal Rising demonstrators were reported to have been on the track, with at least two affixing themselves to a jump using glue and lock-on devices, according to the climate and animal rights group.

Following a fatal fall at the first fence, racehorse Hill Sixteen died after the race had finished, according to Sky Sports News. According to the animal rights group, this is what the protest was trying to stop.

"We are continuing to work with The Jockey Club and other partners to keep people safe during the Grand National Festival," Merseyside Police said.

"We are aware of people who planned to protest at today's 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."

Student Sarah McCaffrey, who was one of those disrupting the track said: "I know everyone coming to Aintree to view the races today would say they love the horses; however, the suffering experienced by them should shock us all.

"That's why I've decided to put my body between those horses and death on the racecourse, rather than gamble with their lives."

A number of individuals also sat on the M57 motorway, which runs from the M62 to Aintree. Police stopped traffic in both directions causing delays for more than an hour.

When the race got under way it was Corach Rambler, ridden by Derek Fox and trained by Lucinda Russell that stormed to victory to win the race, which lasted around 10 minutes.

"Today marks not the end, but the beginning, of the summer of Animal Rising," spokesperson Orla Coghlan said.

"We will be defending animals and nature and creating an un-ignorable national conversation about our relationship to animals and the natural world."

Read more:
Animal Rising protesters say they'll try to stop Grand National
Opinion - 'I loved the Grand National until I saw what I saw'

Earlier, the animal rights group announced plans to prevent the steeplechase from starting, with up to 300 activists planning to scale fences and enter the track.

It said: "We will be slow marching around the perimeter and at some point we may peacefully try to make our way towards the track, again to prevent this race from happening because we know horses are being harmed."

Ahead of the Grand National race, three people were arrested on suspicion of conspiracy to cause a public nuisance, including 25-year-old spokesperson Claudia Penna Rojas.

A man and a 33-year-old woman were detained in Greater Manchester on suspicion of the same offence.

Some racegoers did not seem to notice the delay caused by the presence of protesters.

Alice Pocock, 29, from Newbury, Berkshire, said: "All my friends messaged asking if we'd seen the protesters but we didn't notice, I just wondered why the race was delayed.

"Every horse here is born and bred to race. I think the protesters are putting themselves at harm and they don't understand the racing industry."