Two members of an animal rights group have been sentenced for their roles in a decade-long campaign of intimidation in which researchers were targeted with incendiary devices, false allegations of paedophilia and packages claimed to have been contaminated with HIV.

British woman Natasha Simpkins and Dutch husband Sven Van Hasselt were part of Stop Huntingdon Animal Cruelty (Shac), which aimed to shut down a British animal testing company by terrorising its staff, suppliers, and business partners across Europe.

Van Hasselt, 31, was jailed for five years and Simpkins, 30, was given a two-year prison sentence suspended for two years after they admitted conspiracy to blackmail at Winchester Crown Court.

Michael Bowes QC, prosecuting, told the court that Van Hasselt was personally involved in setting fire bombs which destroyed sports cars and other vehicles belonging to employees of companies linked to Cambridge-based Huntingdon Life Sciences (HLS), which runs Europe’s largest animal-testing laboratory.

Their aim was to put HLS out of business by harassing supply companies into cutting ties with it.

The campaign also included the desecration of a grave and theft of an urn belonging to the mother of one employee, Mr Bowes said.

The series of attacks, which happened in France, Switzerland and Germany during 2008 and 2009, included paint stripper being daubed on cars and graffiti sprayed at employees’ homes warning: “Drop HLS or you will be dead.”

Mr Bowes said that the use of incendiary devices was an escalation of the tactics used by Shac, whose activists also made hoax bomb threats, blocked email and phone systems, and sent sanitary towels they claimed carried HIV to staff.

He said Simpkins took part in criminal damage in Dusseldorf, Germany, and was involved in communications on behalf of Shac with blackmail target Swiss pharmaceutical company Novartis, a supplier of HLS.

She worked alongside Shac ringleader Debbie Vincent, who was jailed for six years in 2014 for her part in the conspiracy.

Natasha Simpkins was sentenced to two years in prison suspended for two years

Mr Bowes said: “Throughout the period late 2008 – August 2009 there was then an intensive criminal campaign in Europe against, in particular, Novartis.

“The criminal acts perpetrated in Europe in furtherance of the conspiracy involved an escalation in seriousness by the use of real incendiary devices resulting in arson attacks and a grave desecration.”

Simpkins and Van Hasselt were arrested in Amsterdam in 2012 following an investigation by Metropolitan Police counter-terrorism detectives.

The two defendants, who have been recently living in Bournemouth, Dorset, were extradited from the Netherlands after being tried there for their part in a liberation attack on a mink farm which set loose 5,000 animals.

Adrian Waterman QC, defending Van Hasselt, said that he suffered from Asperger syndrome and had been treated for mental health problems in his youth.

He said that he was a “troubled soul” and added: “He regrets it and cannot fathom how on Earth he came to be involved.”