A Cambridge University security man told a court how he tried to stop a protester heckling Chinese Prime Minister Wen Jiaboa during a lecture because "freedom of speech was being disrupted".
"Proctor" Paul Beattie told the district judge sitting at Cambridge Magistrates' Court that university regulation did not allow lectures to be disrupted.
He said he removed Martin Jahnke from a lecture hall where the Chinese Premier was speaking after the medical research student refused to stop shouting.
Jahnke, 27, a German studying at Darwin College, Cambridge, denies using words or behaviour likely to cause harassment, alarm or distress to Mr Wen or others in Cambridge in February.
The court has heard that Jahnke disrupted the Chinese PM's lecture by blowing a whistle, calling him a "dictator" and accusing university bosses of "prostituting" themselves by allowing him to speak.
He then took off one of his training shoes and threw it towards the stage where the Chinese leader was standing.
Prosecutors say the shoe landed a few yards away from Mr Wen but could have caused serious injury.
Mr Beattie told the court he went into action after hearing Jahnke blow a whistle and begin shouting.
"I was responsible for freedom of speech and freedom of speech was being disrupted," he said.
"I believe I asked the person shouting to be quiet and sit down. They carried on shouting."
Mr Beattie added: "He was disrupting a university lecture and that is not permitted under university regulations.
"I took hold of his jacket and pulled him to the end of the row."
He said Jahnke was later arrested by police.