Geronimo the alpaca has been killed after a court-ordered destruction warrant was carried out on the animal following its positive test for bovine tuberculosis.
The fate of the eight-year-old alpaca has dominated British media in recent weeks with public pleas from its owner and high-profile celebrities to save him.
However, the UK's Department for Environment, Food and Rural Affairs confirmed the death of the animal on Tuesday.
In a statement, the public body said staff from the Animal and Plant Health Agency (APHA) had euthanised the animal as "a necessary measure to control the spread of bovine tuberculosis".
Geronimo's owner, Helen Macdonald, and protesters had shown up at her farm to guard him from executioners. More than 140,000 people had signed a petition calling for the animal to be saved.
Ms Macdonald, a veterinary nurse, said the alpaca was negative when he was brought in from New Zealand and she had spent thousands of pounds on a failed court battle to save him.
A spokesman for the prime minister said it is highly distressing for someone to lose an animal.
"Our sympathies are with Ms Macdonald and others that are affected by this terrible disease," he said.
Chief Veterinary Officer Christine Middlemiss said: "This is a terribly sad situation and our sympathies remain with all those affected by this devastating disease.
"No one wants to have to cull infected animals if it can be avoided, but we need to follow the scientific evidence and cull animals that have tested positive for bTB to minimise spread of this insidious disease and ultimately eradicate the biggest threat to animal health in this country.
"Not only is this essential to protect the livelihoods of our farming industry and rural communities, but it is also necessary to avoid more TB cases in humans."
Bovine tuberculosis is a highly infectious disease that can spread to cattle and other mammals, costing the UK taxpayer £100 million ($138m) each year.
In 2020 alone, more than 27,000 cattle had to be slaughtered to curb its spread, Defra claims.
A postmortem examination will now be carried out by veterinary pathologists and will be followed by a bacteriological culture of selected tissue samples, which can take up to three months.