Four animals rights activists were found guilty today of blackmailing companies who supplied Huntingdon Life Sciences.
Gerrah Selby, 20, Daniel Wadham, 21, Gavin Medd-Hall, 45, Heather Nicholson, 41, and Trevor Holmes, 51, were alleged to have orchestrated the campaign which ran between 2001 and 2007, Winchester Crown Court heard.
All five denied conspiracy to blackmail but Selby, Wadham, Medd-Hall and Nicholson were found guilty today. Holmes was cleared of the charge.
One of the jurors refused to be seen in court while the verdict was announced after 33 hours and 48 minutes of deliberation.
Sentencing will take place on 19 January at Winchester Crown Court.
Selby, Wadham and Medd-Hall were released on conditional bail, while Nicholson was remanded in custody.
Three other people - Gregg Avery, Natasha Avery and Daniel Amos - have pleaded guilty to conspiracy to blackmail.
The hierarchy of the group called Stop Huntingdon Animal Cruelty (Shac) used threats such as claiming that managers of the companies were paedophiles, hoax bombs parcels, criminal damage and threatening telephone calls to force them to cut links with the animal testing company.
The aim was to target suppliers or any company with a secondary link with Huntingdon Life Sciences (HLS), based in Cambridge.
One of the features of intimidation included sending used sanitary towels in the post, saying they were contaminated with the Aids virus, and personal campaigns against the management of companies including daubing roads outside their homes with words like "Puppy Killer".
Nicholson, from Eversley in Hampshire, was a founder member of Shac, who managed the "menacing" campaigns against the firms who were named on the group's website.
The blackmail would only stop when they put out a "capitulation statement" to Shac saying they would not supply HLS, which conducts animal testing for the pharmaceutical industry, the court was told.
Medd-Hall, from Croydon in south London, was a computer and research expert high up in Shac who uncovered company links with HLS.
Wadham, from Bromley, south east London, joined Shac in 2005 and was in regular attendance at demonstrations against the firms and HLS.
Selby, from Chiswick in west London, was also a regular activist at demonstrations in the UK and Europe, including a violent demo in Paris.
Holmes, from Newcastle upon Tyne, was alleged to be a senior member of Shac who took part in criminal damage in the UK, the court heard.