Fourteen animal rights protesters were acquitted following a month-long trial, after the judge ruled that police had acted unlawfully to stop their demonstration.
The activists were cleared of disobeying police orders when demonstrating at Oxford University's Encaenia ceremony outside the Sheldonian Theatre in June 2006.
During the trial at Bicester Magistrates' Court, a taped conversation between police officers was played that referred to members of animal rights group Speak as "c***s". The conversation, recorded when a dictaphone was accidentally switched on without the officers' knowledge, included comments that officers wanted to "prosecute the shit out of them".
One officer boasted to colleagues that activists were powerless to fight against the University. "The problem is, the protesters do not realise how powerful the University is," he said. "It's a sleeping giant, it's got masons, it's got you...(it has) influence with MPs, masons, barristers."
Other comments recorded on the tape led to accusations of collusion between the police force and the University. The officer states that the "feedback from the University (about the arrests) was... that they were really impressed with it". Another police officer replies: "Well that's the main thing isn't it."
The same officer later added that he felt "deep joy" when he heard that Speak leader Mel Broughton's car had been given a parking ticket following his arrest. He also used the phrase "persecute him, wage a dirty war" in reference to Broughton, while also labelling him "a cock".
Another officer is heard on the tape as saying: "We knew we were going to take bodies today. We knew that was going to happen."
Two officers, including a chief inspector, discussed encouraging people with double pushchairs to walk around the protesters so they could be arrested for obstruction.
He added: "They (Oxford University) have also got more evidence for their review of their injunction. Every time they review it they can say, well actually you can't be trusted to behave."
Five arrests were made while the remaining protesters were led away from the Sheldonian Theatre. One officer described the police actions as "a bit of a sledgehammer to crack a nut", while the chief inspector used the term "draconian".
Following the arrests, a police superintendent was recorded as saying: "Now we prosecute the shit out of them."
District Judge Deborah Wright cleared all 14 defendants of offences under section 14 of the Public Order Act. She ruled that the offences had been imposed unlawfully, the recording having showed that police officers planned to make arrests from the outset.
In her ruling she stated, "Although the (recorded) conversations were made away from the public, all the officers were on duty." The judge also criticised the police for placing the protesters under "a metaphoric microscope" that included four officers filming the protesters, one taking still photographs and several acting as spotters.
"Only lip-service was paid to one of the (police) objectives, namely to facilitate legal protest. There was nothing in the demeanour of the protesters to suggest that they would be disorderly. Whoever was responsible for making the decision that this prosecution should proceed in light of the tape may well have made a serious error of judgement," she said.
Speak co-founder Mel Broughton called for an investigation into what he believed was evidence of "police corruption". Referring to police comments about the University, he said, "These two extremely powerful institutions are prepared to get into bed with each other to frustrate lawful protest."
He added that their relationship was "unnaturally close" and "aimed at stopping any opposition at all. One can only be very, very worried at that sort of development. I'm very angry at the way the police have behaved but it's fitting a pattern of police behaviour."
Robert Cogswell, also co-founder of Speak, added: "At Speak we will be insisting on high level talks with Thames Valley Police officers in order to make sure that this sort of political and clearly biased policing is a thing of the past."
A spokesperson for the University said that while the University is in contact with the police force, the relationship is not inappropriate. "The University continues to cooperate with Thames Valley Police to ensure that its students and staff can carry out their everyday activities without fear of intimidation or harassment.
"While we are in regular dialogue with the police, operational matters are entirely within their jurisdiction, and are not a matter for the University," he said.
Deputy Chief Constable Alex Marshall also claimed that the police force was not unduly influenced by the University, saying: "I am confident that the way our organisation works with the University is entirely impartial. Whilst a dialogue between both organisations is essential during such a long-term, high profile and resource intensive operation, retaining Thames Valley Police's independence is crucial.
He added: "I expect professionalism from my officers at all times and those involved have been advised accordingly. The language and nature of some of the comments are regrettable."
Marshall has promised to review the case to consider disciplinary action against the officers involved.
At the end of the court case two of the protesters, Pauline Broughton and Fran Cornwell, were convicted of obstructing and assaulting a police officer. However, the judge handed down an absolute discharge in both cases, awarding the defendants 75 per cent of their legal costs.
Mel Broughton said: "I hope someone, somewhere is going to make the very brave decision to investigate these officers thoroughly. I am certainly going to be looking at taking our own proceedings against the police. If the system in place won't do anything about it then we have to defend our basic rights - we are going to have to look for a way of doing it ourselves."