Oxford University has resumed building work on its controversial new laboratory complex on South Parks Road.
The vast majority of the animals used in the new centre will be rodents
Construction work on the biomedical facility had been halted in July 2004 after a sustained campaign of protest from animal rights groups.
The building contractor, Walter Lilly & Co, said its staff had been subjected to threats and intimidation.
The university has now engaged a new company and work on the £20m complex began early on Wednesday.
Oxford said it was determined to finish the project, which is now well behind schedule.
"The new biomedical research building will provide world-class facilities reflecting the university's commitment to animal welfare and to scientific progress," added David Holmes, the institution's Registrar.
"Completing the project will be good for animal welfare, good for medial research and good for the treatment of life-threatening conditions all over the world."
Mr Holmes confirmed that the government had been supportive and that assistance had been given by Thames Valley Police. He added that the £20m construction cost did not include security costs for the site.
The facility was first conceived a decade ago; it has been in detailed planning for over five years and phase one of the project was originally to have been completed this Autumn.
It is designed to replace existing university animal housing and laboratory space in a single, modern complex, stressed Mr Holmes.
"Contrary to some reports, this building does not constitute an expansion in animal research at Oxford," he told a news conference in London.
The university has obtained a high court injunction to limit demonstrations to one day a week with not more than 50 protestors.
Adolfo Sansolini, chief executive of the British Union for the Abolition of Vivisection (Buav), said his organisation was opposed to the harrassment and intimidation used by some protestors and "equally opposed to the violence of vivisection".
"We are disappointed to see that Oxford university are resuming building their new laboratory complex, still wedded to the animal model of research, despite evidence that it is failing, irrelevant and outmoded," he commented.
Robert Cogswell, from the animal rights group Speak, has said his organisation will keep fighting the university.