From mid-afternoon they came, in their hundreds, to the gates of Television Centre, waving banners, lighting flares and chanting "BBC! Shame on you." 50 police officers guarded the entrance, but were unable to stop a group of about 25 protestors from breaking through and into the building. They were quickly removed.
Other demonstrators grabbed officers' helmets and threw them into the crowd. Wooden poles that held placards were thrown at the four-deep cordon of police. By the time filming began at around 7.30pm, six people had been arrested and three police officers had been injured. One was taken to hospital with a head injury.
The protesters continued to chant outside throughout the filming and separated with the intention of covering every exit when Nick Griffin left.
When members of the audience began to file out, many said Mr Griffin had performed badly. David Kernohan, 26, of King's Lynn, Norfolk, said: "By the end, the audience were essentially ridiculing him and shouting things at him. He was obviously very nervous. I don't think he would be pleased with the performance.
"I think he made a fool of himself and will have turned moderate people off the party. It was excellent – a good day for democracy."
Shimal Thakrar, 33, from Edgware, London, said the audience hissed and booed during the filming and shouted "liar" and "get out the door" at Mr Griffin.
Some audience members reported that "two or three" others had been vocal in their support of Mr Griffin after filming had finished.
Another said that he had not been impressed by Mr Griffin's performance because the BNP leader had been inconsistent in his answers. Josh Gordon, 21, from west London, said: "Griffin's points were listened to but he was challenged on some things he had previously said. He tried to distance himself from his quotes on the Holocaust. He had some of his past quotes read to him but he claimed he had been misquoted."
Andrew Slater, 21, said: "The only thing Griffin said which was not roundly opposed was that he agreed with the Tories' proposal for a points-based immigration system. But when it came to the debate on his racial policies, what an indigenous Britain is, for example, he had most of his platform destroyed by the other panellists."
Those at the filming had their mobile phones confiscated and were made to pass through X-ray machines before entering the studio. Several audience members said they thought the protest outside had not been necessary.
Martin Smith, the Unite Against Fascism organiser, who directed protesters to the gate at Television Centre through which many surged, had vowed to resist police attempts to break up the demonstration and insisted it was essentially peaceful. But he did admit that one far-right supporter had been attacked earlier in the afternoon. "A guy came with a BNP banner. That was ripped from him and he was hit on the head, but you have to expect that if you come to an anti-fascist demonstration with a BNP banner," said Mr Smith.Reuse content