Each day Jeffrey Gray, a professor of psychology at the University of London, looks under his car for bombs. As he drives to work his eyes flick to the rear mirror to check whether he is being followed.
The precautions are sensible, although he works in a profession that most would not associate with the security measures taken by soldiers. Gray has reason to believe that an animal rights terrorist wants to kill him.
His "crime" is to have used rats in experiments during 20 years of research into brain damage, memory loss and Alzheimer's disease.
"It's not paranoia. I know I'm on a hit list," said Gray. His entire department lives with the threat. In the past a colleague has found a bomb under his car. This month a lab technician was threatened.
Two car bomb attacks on veterinary surgeons within a week have only intensified a feeling among the 18,000 British researchers licensed to carry out experiments on animals that a new anti-science movement is gathering momentum. Yesterday police were investigating another suspected attack with a petrol bomb on a meat trade supplier's van in Portsmouth.
Gray said: "Its supporters have shrouded themselves in a 'green' mystique. They cannot see the moral incoherence of acts of violence against humans made in the name of animals."
The bombings have polarised animal welfare groups. While mainstream groups such as the British Union for the Abolition of Vivisection condemned the violence, others welcomed it.
Vivien Smith, one of the Animal Liberation Front's leading activists, insisted last week that the bombers were no longer interested in winning public support for their cause. "I would not have felt remorse if the intended targets had lost their lives," she said. "I certainly would not have lost any sleep over it."
A fellow activist, Ronnie Lee, the former leader of the ALF now serving a 10-year jail sentence for arson, has helped her edit "Arkangel", a new magazine celebrating bombings, from his cell at Channings Wood prison, Devon.
An anonymous report in the latest issue calls for the ALF to learn from the tactics of the IRA. "They have advanced from being a floundering peasant army equipped with primitive tools and a few weapons to an extremely well-equipped, effective, serious threat to their enemy," it says. "As it goes into the 1990s the animal liberation movement needs to grow up - the childish games must stop."
Detectives believe that two car bombs, at Porton Down and Bristol, were primed to explode at the same time. This weekend, John Cupper, 13 months, who suffered shrapnel wounds and a partially severed finger in the Bristol blast, is recovering from his injuries in hospital.
In each attack, PE4, a plastic explosive, was used in conjunction with a mercury tilt trigger. The explosive, made by the Royal Ordnance solely for military use, is identical to that used last year in the bombing of Bristol University's senate house.
Few scientists who have any connection with animals are safe. Last week Professor Duncan Walker, a surgeon who used tissue from a pig's heart to save the life of a seven-month-old boy, received death threats.
Scientists such as Gray are saddened and angered by the campaign of intimidation. "I'm extremely proud of my work. I feel entirely happy with it and the way it is carried out. I have no qualms about defending it," Gray said.
"The tragedy is that we are entering into an era of silence because scientists are scared of speaking out and becoming targets."
Universities and drug companies are becoming especially vigilant. SmithKline Beecham, one of the biggest pharmaceutical companies in Britain, has sent letters to 2,000 staff giving advice on how to spot car bombs.
In the meantime, the scientists have been gradually reducing the number of animal experiments. Figures to be published by the Home Office show the number of animals used in experiments has fallen for the thirteenth consecutive year. Last year 3.2m animals were used, a drop of 6 per cent.
Medical advances, refinement of techniques and pressure from the animal welfare lobby have brought a steady decline since 1976, when 5.4m animals a year were used.
Under the 1986 Animal (Scientific Procedures) Act, which came into force this year, all scientists are obliged to assess the degree of suffering an experiment is likely to inflict and balance it against the likely benefit.
However, even though the law is one of the most comprehensive animal welfare acts in the world, its enforcement is coming under increasing criticism.
Last month, Professor Wilhelm Feldberg, 89, an eminent scientist, handed back his licence after he was filmed cutting into a rabbit that had not been fully anaesthetised. The cruelty occurred even though Home Office inspectors had visited his laboratory at the National Institute for Medical Research in London four times in the past year and had spent six months discussing whether his work should end.
The recent introduction of a code on the use of live animals in research is expected to lead to a severe reduction in the number of animals used. Universities and veterinary colleges say they cannot afford to meet its demands for improved housing. The cost of implementing the code exceeds ú75m, while the University Grants Council (UGC) can only budget for ú10m. A dozen institutions need more than ú1m worth of work each to bring them up to standard within the next two years; Cambridge alone needs ú9m.
Sir Peter Swinnerton-Dyer, chief executive of the UGC, said: "It's a grave problem. I have not the faintest idea where the money is going to come from."
The use of primates in experiments will come under renewed critical scrutiny next month with the publication of a report by the RSPCA and the Fund for the Replacement of Animals in Medical Experiments, a registered charity.
Their survey of more than 200 experiments using primates in the four years to 1988 criticises researchers for not revealing what had actually been done to the monkeys, how they were cared for or where they had come from.
One of the authors, Dr Judith Hampson, a member of the Home Office procedures committee, said: "In some cases it appeared that researchers were using odd, spare primates left over from someone else's experiment. That's not good science, and it's a waste of a life."
While scientists insist that many areas of medical research necessitate work on live animals, there is increasing development of techniques which are reducing the need for animals in basic tests. For example, chemical analysis now replaces the injection of mice in testing insulin.
Last week one senior member of the Home Office procedures committee, who declined to be named for fear of reprisals, admitted that long-term toxicity tests on animals had been shown to be largely unnecessary. In many cases, a six-month test can reveal as much as one lasting a year.
For some research, however, there can be no substitute for live tissue, according to Professor Colin Blakemore, who has endured a campaign of vilification for his pioneering work on vision. He remains a staunch defender of the right of scientists to work on animals.
"I don't know anyone who works with animals who enjoys killing them. If there were alternatives, we would use them," he said.
"The current campaign of hatred is the natural escalation of 10 years of animal rights propaganda. People are terrified. I am petrified for myself and my family."
