Geronimo the alpaca has tested positive for bovine tuberculosis (bTB) twice, and last week the High Court ruled that the Department for Environment, Food and Rural Affairs (Defra) had a 30-day window starting on August 5 to legally slaughter the animal.

However, Geronimo’s owner, Helen Macdonald is disputing the validity of the bTB tests used on her alpaca, and told The Telegraph last night that her last hope is for the Prime Minister to intervene, and that she “would love Carrie’s support” on this issue.

Demonstrators will march on Westminster on Monday in the animal’s name and organiser Dominic Dyer has joined Ms Macdonald in her call for the Prime Minister’s wife to weigh in on Geronimo’s behalf.

Mr Dyer, former head of the Badger Trust, told The Telegraph that he plans to call on Mrs Johnson to use her “significant influence” and join the bid to save Geronimo when he addresses protesters on Monday.

Back at her farm in Wickwar, near Bristol, Ms Macdonald says a group of peaceful activists will form a “human shield” around Geronimo, in case Defra contractors arrive to slaughter the animal with the distraction of the protest in the capital.

“This is about Geronimo’s life, he’s a sentient human being. But it is also about my life and my family’s life,” said Ms Macdonald. “My mum is 84 today. And she has asked me, ‘Are they going to shoot Geronimo on my birthday?’”

The “Save Geronimo” protest will start at Defra headquarters, and march on to Downing Street. It is expected to include members from the British Alpaca Society, Badger Trust, and other animal rights groups.

Mr Dyer told The Telegraph that he wants Mrs Johnson, pictured below, to intervene because she “has a track record” on speaking out on issues of animal welfare.

Mrs Johnson is director of communications at the Aspinall Charity - a British charity “dedicated to returning captive bred animals to protected wilderness” and is a patron for the Conservative Animal Welfare Foundation (CAWF), which is an organisation independent from the political party “which seeks to help advance farm animal welfare” and was established in 2016.

Geronimo’s supporters want the alpaca to be tested again, this time using a PCR test - which looks for the presence of the TB bacteria in blood - before he is killed, believing that this test may be more accurate than those used on him to date.

Christine Middlemiss, the Chief Veterinary Officer,  said on Sunday night that while she was sympathetic to Ms Macdonald’s situation, the accuracy of the tests used to diagnose Geronimo should not be in question.

“The tests used on Geronimo were developed for use on alpacas and are highly specific – the chances of a false positive are significantly less than one per cent and we have tested him twice,” she said.

A spokesperson for Defra said “bovine tuberculosis is one of the greatest animal health threats we face today and causes devastation and distress for farming families and rural communities across the country while costing the taxpayer around £100m every year.

“Therefore, while nobody wants to cull infected animals, we need to do everything we can to tackle this disease to stop it spreading and to protect the livelihoods of those affected.”

The Telegraph has contacted Mrs Johnson’s spokesman for comment.