Dozens of police officers will flood into Oxford city centre tomorrow to ensure there is no trouble during a demonstration by animal rights protesters.
Police say they have been forced to deploy large numbers of officers to "cope with every eventuality", because organisers have not given them information about the scale or nature of the demonstration.
The protest by animal rights group Speak, which is advertised on its website, is the latest in a series of demonstrations and marches against Oxford University's construction of a research laboratory in South Parks Road. Thames Valley police's Oxfordshire Commander, Chief Supt David McWhirter, said: "We believe this demonstration will be different from previous events as the group have stated they don't plan to hold a march or procession.
"However, as the organisers of the event have not worked with us in preparation for Saturday, we do not have exact details as to what they will be doing."
Speak spokesman Mel Broughton said he did not expect large numbers of people at the protest and claimed any lack of cooperation was due to the way Speak had previously been treated by the police.
He said: "We have decided we are not going to negotiate with the police, a, because we are not planning a march and b, because of their behaviour at the demonstration on January 21 when they reneged on their promise to let us march up to the site of the laboratory."
The demonstration is due to start at noon tomorrow, and Mr Broughton said he expected the protest to last all afternoon.