The 46-year-old has committed crimes for his passionately held beliefs and now he is ready to die for them.

Jailed for arson in 1996, Horne has been on a hunger strike since 6 October in protest at the use of animals in medical experiments and the government's failure to set up a Royal Commission on the issue.

It is the third time he has refused food since being imprisoned - the first lasted 35 days, the second 46.

Hunger strike revival

He is not alone in his self-inflicted torture. Hunger-striking seems to be back in vogue as a means of protest.

Ilich Ramirez Sanchez, better known as Carlos the Jackal, has just ended a 20-day hunger strike. Once one of the world's most wanted terrorists, he was protesting at being held in solitary confinement at La Sante prison in Paris for the past four years.

Dr Jack Kevorkian, the 70-year-old retired pathologist, charged with first-degree murder after being shown on television administering a lethal injection to a terminally ill patient, says he will starve for his beliefs if he goes to jail.

He has acknowledged he played a role in some 130 assisted suicides since 1990.

British aid-worker, Sally Becker, dubbed the Angel of Mostar for her humanitarian work, went without food or water for a week in Kosovo prison in protest at a 30-day sentence for illegally crossing the Albanian-Yugoslav border while trying to help refugees.

The list of hunger-strikers in recent months also includes Algerian journalists, militant Tibetan exiles and a prisoner in Oxfordshire who is refusing to eat anything other than a vegan diet.

Maze protest

In the UK, the most well known case of hunger striking claimed the life of Bobby Sands. An H-Block IRA prisoner, he began a hunger strike in support of political status on 1 March 1981.

His death on 5 May after 66 days of fasting prompted riots on both sides of the Northern Ireland border. There were 100,000 at his funeral.

Sands was the first of 10 IRA and Irish National Liberation Army (INLA) prisoners to die for the right to be considered prisoners of war rather than criminals.

Scientific study

Studies into self-imposed starvation were conducted during World War II.

Dr Ansel Keys reduced the food intake of a number of conscientious objectors, effectively inducing in them an experimental anorexia before returning their food levels to normal.

He demonstrated that individuals whose weight decreases significantly undergo a variety of physical, emotional, and behavioural changes.

A painful way to die

More than 50 days into his protest, Barry Horne's supporters say he is perilously close to death.

While scientists say the length of time that humans can survive without food depends on many factors, Dr Hilary Powers, a senior lecturer in nutritional biochemistry at the University of Sheffield says 60 days is about the endurable limit.

"It depends entirely on how much fat content an individual has their state of health from the outset, but a healthy adult, that's someone who has 11kg of body fat and proper muscle mass could survive for about 60 days," she said.

When the body is deprived of food it starts to use its own tissues to produce energy. It starts on fat stores immediately, but as fat is used it begins to use protein from skeletal muscles and vital organs.

"The body will slow down while trying to conserve protein," Dr Powers said.

"But there will come a point where slowing down is not enough and the situation will become serious. The body will start to break down the protein in vital organs and the heart, respiratory organs and liver will start to fail.