The principle that everyone is entitled to their say, however obnoxious their opinions might be, was put to the test at the Oxford Union last night as hundreds of protesters gathered to voice their disapproval of the two men from the extreme right whom the illustrious debating chamber had invited there to speak.
One of the guests, the BNP leader Nick Griffin, heads an organisation that wants to see millions of people deported from the UK because they do not regard them as truly British.
He was due to share a platform with the historian David Irving, who has courted notoriety for decades by claiming that Hitler did not give the order to commit genocide, that there were no gas chambers and that six million Jews were not killed by the Nazis.
Scuffles broke out as anti-fascist groups yelled "Shame on you" at members filing into the union building, and the police shut the gates with the chamber only half full. While a handful of students crushed against the main gate to create a diversion, 30 others scaled the wall and barged past the tight security, occupying the area around the debating table until they were persuaded to leave.
"I hope we're not giving Griffin further publicity by doing this," said Peter Simpson, a student at Essex University who stormed the chamber, "but history has shown that you need to draw the line with fascists. I think a lot of people are here because they know what happened in the Second World War and they don't want it to happen again."
Dr Evan Harris, the Liberal Democrat MP due to join the debate, criticised Thames Valley Police for "failing to put a cordon around the Union", allowing the protestors to barge through.
"The failure of the police is outrageous," he said as he told students in the chamber of plans to split the speakers after the university authorities decided it was too dangerous to walk Mr Griffin and Mr Irving across the quadrangle to the debating hall.
"The police have failed to provide for the safety of this event; failed to provide for the safety of this going ahead as planned.
"I'm very disappointed. The police imply that they don't have enough resources to move people away from the perimeter or that it is not their job."
In order to get the debate under way, the speakers were split into two groups, with Mr Irving, jailed last year in Austria after pleading guilty to Holocaust denial, speaking in the main chamber, and Mr Griffin, convicted of incitement to racial hatred over material denying the Holocaust in 1998, in a cramped room in the main university building.
Warned to expect a maelstrom of abuse, they had avoided the main demonstration by arriving in separate black cabs, 10 minutes apart and 90 minutes early. The debate – on how far the freedom of speech should extend – finally started more than an hour late at 10pm.
Mr Irving defended accusations that his publications and speeces denied the existence of the Holocaust. "I still refuse to be bowed. I am not going to write what they want me to write. I'm going to write what I find in the archives," he said.
Across the yard, Mr Griffin went head-to-head with two student debaters. "The majority of racist attacks are on white people by members of ethnic minority communities," he said. "Those people outside are a mob and they could kill. Had they grown up in Nazi Germany they would have made splendid Nazis.
"Any restriction on free speech is dangerous. You start by saying people should not speak and you end up with burning people at the stake. Free speech is an absolute, it is universal."
Mr Irving, reported to have left at 10.45pm to a chorus of jeers from waiting demonstrators, said that disagreeing with some elements of the "whole package" did not make him a Holocaust denier. He had been invited to speak at the Oxford Union seven times, he said, but security fears had put paid to any chance of appearing. Speaking at the Union was something he cherished, he added, saying that the most important thing that any student listening to him could do was to think for themselves.
The president of the Oxford Union, Luke Tryl, was unconvinced. "I think David Irving came out of that looking pathetic," he said "I said in my introduction that I found his view repugnant and abhorrent because I wanted that on record."
Outside, some protesters chanted "Kill Tryl", to which the Union president said: "I don't think they do their cause any favours by inciting violence. That is my only regret."
Last night's meeting breached an unwritten agreement observed for years by the mainstream political parties – not to give the far right a public platform. Instead, it fell back on a much older principle, summed up in a maxim attributed to the French philosopher Voltaire: "I disapprove of what you say, but I will defend to the death your right to say it." Mr Tryl, who has been under intense pressure to cancel the event, defended the decision to go ahead. He said: "David Irving and Nick Griffin have awful and abhorrent views but the best way to defeat those views is through debate.
"I remain committed to the principle that free speech has to prevail. I really worry about how the far right has been able to portray themselves as free-speech martyrs and I hope that this sort of debate will help dispel that myth – to show that the liberal mainstream are prepared to take them on and beat them in debate."
A minority of the students gathered outside the building agreed with Mr Tryl. Kudzh Ranga, a black law graduate living in the city, said he supported the right of Mr Griffin and Mr Irving to speak. "Though I don't agree with [Mr Irving's] stance on racism and the Holocaust I think it is only proper to let him come and address the general public," he said.
But most students and protesters in the street vehemently disagreed. They included Jean Kaigamba, a survivor of the Rwandan genocide. He said: "I'm flabbergasted that people who claim to be intellectuals invite extremists in the name of free speech to give them a platform and let them air their perverted view."
David Green, a former committee member of the Oxford Union, said he had resigned from the organisation in protest. "What the union is doing today is extremely irresponsible – namely giving prominence to Holocaust deniers, people who are completely discredited," he said.