A Norfolk farmer whose land neighbours the Sandringham estate has demanded activists who nabbed three of the King's lambs must face the full force of the law.

David Cross, 35, a sheep farmer close to the royal estate - has decried the opportunistic activists as simple thieves. 

"They need to be prosecuted as criminals just like everybody else because they stole property that doesn't belong to them," he said.

The three activists, from the Animal Rising group, filmed themselves going on to Appleton Farm, at West Newton, to take the lambs on Wednesday night. 

READ MORE: Animal activists steal lambs from King's Norfolk estate

The lambs have not yet been returned, despite the trio handing themselves into police earlier today.

"Hopefully they get a decent sentence for the crime and the lambs are returned," Mr Cross said.

Animal Rising said the three women acted on "bravery and compassion" for the animals but the farmer issued a stark warning. 

"We can only hope they didn't steal the lambs from their mother before they've built a strong immune system and are no longer weened because it could be disastrous.

"The activists have no idea what they're doing."

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The group said on its website that the incident "marks the first" of its "high-profile 'open rescues' this summer".

"My personal opinion is that they're after attention because of who they stole the lambs from," said Mr Cross.

"They can try and justify it by claiming to be within a different moral class but all they're doing is stealing things."

"The best we can do is try and minimise the conversation around their agenda so thing's like this don't continue to happen."

The three remain in custody after handing themselves into a Berkshire police station, saying they "stand by the belief that a jury of ordinary people will take the side of care and freedom".