Hundreds of animal rights activists marched through Oxford in protest at a new animal testing laboratory.
About 500 protestors turned out in the streets of Oxford
Saturday's rally, organised by the pressure group Speak, is thought to be the biggest since Oxford University announced plans for the £18m centre.
Dozens of police and private security officers were brought in to ensure the rally passed off smoothly.
Thames Valley Police criticised protestors for holding the rally at a time of high security fears.
Supt Paul Sullivan said: "I am disappointed that Thames Valley Police had to deploy significant numbers of officers to the march to ensure it passed peacefully, with minimal disruption to the city and to others.
"Our officers' time could have been better spent carrying out their usual duties and reassurance especially with the current national security situation."
Work on the South Parks Road site stopped last July when builders Walter Lilly and Co pulled out of the project.
Despite the setback, university chiefs have said they will complete the project.
The university said the centre would replace existing sites and would not mean an increase in animal tests.