An animal rights campaigner has been convicted for the second time of plotting a bombing campaign against Oxford University.

Mel Broughton was involved in the planting of petrol bombs at The Queen’s College’s sports pavilion, off Abingdon Road, and at Templeton College in Kennington to protest against the building of the £20m animal testing laboratory in South Parks Road.

He had twice been tried for the same offence – of conspiracy to commit arson – before yesterday’s unanimous verdict of guilty, delivered by a jury at Oxford Crown Court.

Jurors in the 50-year-old’s first trial in November 2008 failed to reach a verdict but he was subsequently convicted after a retrial in February last year and sentenced to ten years’ imprisonment.

However, Broughton fought the conviction and the Appeal Court ordered a second retrial in March this year, after finding an error in the trial judge’s summing-up.

About £14,000 damage was caused to The Queen’s College building in November 2006.

However, when similar petrol bombs were laid under a temporary building at Templeton College the following February, they failed to ignite.

During the four-week trial, the court was told each bomb was made from two plastic bottles filled with petrol, with three sparkler fireworks used as fuses.

The devices were discovered by security staff following a posting on an animal rights website.

Forensic tests found traces of Broughton’s DNA on the devices.

When police searched his flat in Semilong Road, Northampton, they found details of businesses and people connected with the then partly-built laboratory and 14 packets of sparklers, an Oxford University security pass, a plan of the laboratory and a battery connector.

He denied involvement, saying he had matured and did not use violence to protest.

Yesterday, Broughton was again sentenced to ten years in prison, to be reduced by the two-and-a-half years he has already served behind bars.

Judge Patrick Eccles said he need not add to his remarks after last year’s verdict, when he told the court: “A real and profound sense of fear has pervaded the lives of very many people here in Oxford as a result of the campaign by individuals who have no care for the feelings or sense of security of the innocent men or women who happened to be associated with the laboratory.

“Your involvement in this conspiracy has made a significant contribution to that fear.”

After yesterday’s hearing, Det Supt Mark Jones, who led the investigation, said: “Broughton’s interest in the animal rights cause went further than that of a legitimate protester.

“He has been proven to be someone who believes direct action, in the form of planting explosives and setting fires, is acceptable.

“By doing so, he has shown that he is willing to risk the lives of other people.”

Crown Prosecution Service lawyer Denis Burke added: “No matter what your personal convictions are, putting property and lives at risk through the use of incendiary devices can never be justified.

“This case was not and has never been about attacking free speech or the right to protest. The case centred purely on what we alleged were criminal acts.”

Last night, an Oxford University spokesman said: “The verdict should speak for itself.

“We will continue to work with all relevant authorities to protect staff and students from criminal activity of any kind.”