Around 18 months ago, under the title “Defeated but not deterred”, this magazine published an editorial on animal-rights activism in Britain. A campaign of violence and vandalism had just forced the University of Cambridge to cancel plans for a primate research laboratory. Nature suggested then that the victory would not necessarily be repeated. We wish we had been right, but that optimism now looks premature.

The extremists have now secured another success. Darley Oaks is a small family farm in the Midlands. The owners have been breeding guinea pigs for medical research for more than a decade. For the last six of those years, they have suffered a campaign of arson attacks and death threats, and have seen letters of abuse sent to people connected with their business. The campaign culminated in macabre fashion last October, when the remains of a family relative were dug up and removed by protestors demanding that the business close. Last week, the family decided to comply.

It was the second notable victory for the animal-rights extremists since the Cambridge decision. Work on a new animal house at the University of Oxford has been stalled for over a year, after threats and vandalism forced contractors to pull out. The increased support for animal research seen in the media and in public opinion polls, and highlighted in our editorial, has continued during that period. But the activists have become more focused and strategic — and more successful.

Analysis of the new tactics suggests that the fight against the extremists may take longer to win than anticipated. Activists have been concentrating on a small number of secondary targets, such as financial firms that act for animal testing laboratories. Attacks to individuals' homes are common. It is impossible for the police to defend such a wide range of targets and, as a consequence, many companies have ended associations with animal researchers and breeders. And it is not just British researchers who should be concerned: similar tactics are becoming increasingly common in the United States, where the FBI is investigating more than 100 cases, many involving arson.

Yet there is plenty to suggest that the extremists' actions will only prolong their fight, not allow them to win it. New UK legislation, aimed at punishing protestors who set out to cause economic damage to companies, came into force this summer. Perhaps because of publicity surrounding the new offences, attacks on company and private property connected with animal research fell sharply even before the new powers became law.

In the longer term, police must infiltrate the activists as they would any other extremist organization. It is a welcome sign that the UK government has made animal activists a major focus for the National Extremism Tactical Co-ordination Unit, a policing body established in March 2004.

More than 500 prominent scientists have put their names to a declaration released last week that backs animal research.

Action from the research community is the final front in the fight. Here the news is encouraging, although a great deal remains to be done. A decade ago, the Research Defence Society (now known as the RDS), which supports the medical use of animals, could call on just two researchers when asked to supply scientists for media interviews. That number now stands at 25. This is still far too few, given that thousands of researchers in Britain use animals in their work. But it is a start. It is also good to see that more than 500 prominent scientists have put their names to an RDS statement released last week, the Declaration on Animals in Medical Research, that backs animal research.

Perhaps the only group not pulling its weight is the university sector. Some universities encourage researchers to speak out, but they are in the minority. Universities have just as a big a stake in animal research as any other science organization. This reluctance to talk to the public about their research merely plays into the hands of the extremists, who would be delighted to see scientists stay silent.