Activist Mark Taylor has been jailed for a record four years for his part in a campaign of intimidation to stop companies dealing with a firm doing animal experiments.
Mark Taylor drove protesters around the country to companies which either supplied or dealt with Huntingdon Life Sciences in Cambridgeshire.
During three months over the summer of 2005, workers were terrified as up to 12 protesters invaded their offices shouting "Murderers" and insults, the Old Bailey heard.
Taylor, 39, his wife Suzanne, 35, both of Henry Street, Wakefield, West Yorkshire, and Teresa Portwine, 48, of Dunley Drive, New Addington, Surrey, were the first to be charged under new legislation.
They pleaded guilty to conspiracy to interfere with a contractual relationship.
Mrs Taylor was given two-and-a-half years in jail and Portwine was sentenced to 15 months.
The judge said the sentence must be a deterrent to others.