The ringleaders of a group of British extremists who led a lengthy campaign of intimidation against companies and individuals involved in animal testing were sentenced to jail terms of up to 11 years on Wednesday for conspiracy to blackmail.

Heather Nicholson, one of the founders of Stop Huntingdon Animal Cruelty (SHAC), established to close down the UK’s leading commercial animal testing unit, was condemned to 11 years, while Greg Avery and his wife Natasha, the other founders, received 9 year terms after pleading guilty.