The activists sent hoax bombs and made threatening phone calls
Seven animal rights activists who blackmailed companies linked to an animal testing laboratory have been jailed for between four and 11 years.
They used paedophile smears, criminal damage and bomb hoaxes to intimidate companies associated with Huntingdon Life Sciences (HLS) in Cambridgeshire.
Heather Nicholson, Gerrah Selby, Daniel Wadham and Gavin Medd-Hall were found guilty of conspiracy to blackmail.
Gregg and Natasha Avery, of Hampshire, and Daniel Amos admitted the charge.
Winchester Crown Court heard that during a six-year campaign members of Stop Huntingdon Animal Cruelty (SHAC) falsely claimed managers of the companies were paedophiles.
They also sent hoax bomb parcels and made threatening telephone calls to firms telling them to cut links with HLS.
One of the features of intimidation included sending used sanitary items in the post to the firms and daubing roads outside managers' homes with slogans such as "puppy killer".
Members of SHAC covered their faces during a raid
Nicholson, 41, of Eversley, Hampshire, was jailed for 11 years; married couple Gregg, 41, and Natasha, 39, Avery, also from Eversley, were sentenced to nine years each; and Medd-Hall, 45, of Croydon, south London, was given an eight-year prison sentence.
All were given indefinite Anti-Social Behaviour Orders, banning them from travelling to the firms targeted.
Wadham, 21, of Bromley, south London, was jailed for five years while Selby, 20, of Chiswick, London, and Amos, 22, of Church Crookham, Hants, were both sentenced to four years in prison.
The court heard that Nicholson and the Averys were the founders of SHAC, and managed the "menacing" campaigns against the firms.
Sentencing the activists, Mr Justice Butterfield called the campaign "urban terrorism" and a "relentless, sustained and merciless persecution" which had made the victims lives "a living hell".
He said he accepted that the seven had genuine deeply-held beliefs that animal testing was wrong, and had the right to protest against it.
But he told them that companies had the right to conduct vital biomedical research and the right to conduct lawful trading.
He called the leaders "lifelong, veteran, fanatical animal rights activists" and said: "It was a relentless, sustained campaign designed to strike such fear in the minds of employees that the companies would capitulate.
"I expect you will be seen by some as martyrs for a noble cause but that would be misplaced.
"You are not going to prison for expressing your beliefs, you are going to prison because you have committed a serious criminal offence."
The court heard that between 2001 and 2007, SHAC, which was based near Hook, Hampshire, targeted companies in the UK and Europe that either supplied or had secondary links with HLS.
About 40 companies were victimised and the total cost of damage and increased security was £12.6m, not including loss of profits, the court was told.
Det Ch Insp Andy Robbins from Kent Police, who led the £4m inquiry involving five forces, said: "I hope today's sentences provide some comfort and a sense of justice to the individuals and the families who suffered such sustained harassment."
Science Minister Lord Drayson, added: "Those involved in life-saving medical research make a huge contribution to society. They deserve our thanks, support and protection.
Another defendant, Trevor Holmes, 51, from Newcastle, was cleared.
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