So the viewing public was treated to Mr Griffin squirming under direct and angry questions from a BBC audience, evading his past, refuting that he had denied the Holocaust.

Skin colour, he said, was irrelevant when it came to describing the indigenous people of Britain.

“We are the aborigines,” he declared.

Justice Secretary Jack Straw, Tory Baroness Warsi and Chris Huhne of the Lib Dems, who bore down on him at every turn, said race was what Mr Griffin was all about.

“It is that difference -- the fact that the BNP defines itself on race -- which distinguishes it from every other political party I can think of,” said Mr Straw.

But Mr Straw found himself on the spot from the audience to strengthen the laws on immigration, the issue that feeds BNP support. And, despite the humiliation, Mr Griffin and his supporters counted the exposure as a success equal to winning two seats in the European elections.

All day yesterday, as the BNP website counted down the minutes to the party’s appearance as political equals on the most popular current affairs programme on television, it was clear that more than 60 minutes of airtime were at stake.

While liberal voices continued the on-air debate on freedom of speech and censorship both anti-fascists and the far-right grasped that what was being fought for was more than the BBC’s adherence to its rules of impartiality.

By mid-afternoon the BBC headquarters in White City came under siege from protesters, their number undoubtedly swollen by the BBC news channel’s rolling coverage of events on its own doorstep.

About 25 people broke through the security cordon and there were six arrests, but the closest they came to a TV studio was when one protester reported seeing Piers Morgan in the foyer.

There were protests outside other BBC offices, including Pacific Quay in Glasgow. It all delighted Mr Griffin who was able to give a running commentary over the pictures on rival channels, portraying himself as a victim of the baying mob backed by a conspiracy of mainstream parties hours before the programme was recorded.

He teased about whether he would be able to make his way past the protesters but, as arranged, he entered via a side door, surrounded by his own heavy security.

Later, during filming, Mr Griffin was reprimanded by presenter David Dimbleby for smiling as he avoided answering a question over his views on the holocaust.

“Why are you smiling? It’s not a particularly amusing issue,” Mr Dimbleby said.

Fellow panellist, playwright Bonnie Greer, was left open-mouthed as Mr Griffin said he had no answers for a young member of the audience who asked about his views on the holocaust.

“I cannot explain why I used to say those things,” he said. “I cannot tell you any more than I can tell you why I changed my mind. I can’t tell you the extent to which I changed my mind.”

But Mr Straw said as Justice Minister he could “promise” Mr Griffin that he would not be prosecuted if he wanted to explain his views. The invitation was not accepted.

Referring to how the BNP must now change its membership policy to admit people of all races, Mr Griffin laughed again. Ms Greer was cheered by the audience as she said: “You can laugh but if I was a BNP member I’d be scared.”

Huhne accused Mr Griffin of “peddling hatred and fear” and added that “Churchill would be rolling in his grave” -- a reference to Mr Griffin’s claim that the wartime leader would have been a BNP member.

He was cheered as he quoted Mr Griffin as saying Hitler went “a bit too far”.

But Mr Griffin denied saying such a thing -- despite the panel agreeing it was on video -- saying: “I am the most loathed man in Britain in the eyes of British Nazis.”

He was also widely mocked by the panel and audience as he suggested that David Duke, the leader of the Ku Klux Klan, was “almost totally non-violent”

Baroness Warsi said Mr Griffin was “obviously a confused man” and a “thoroughly, thoroughly deceptive man who comes on here and tries to sell whatever message that he wants”.

He was “evasive” in his answers and brings Christianity “into disrepute”, she said.

After one audience member labelled Mr Griffin “completely disgusting”, he claimed he was frequently misquoted by the media and he would agree that he was a “monster” if everything written about him was true. “Those things are outrageous lies,” he said.

Asked which of the quotes in media reports were lies, he said: “The vast majority of them, far too many to go in to.”

Mr Dimbleby repeatedly asked Mr Griffin which of his quotes on race, mixed marriages and Islam were wrong and suggested that the BNP leader could not deny saying them.

But Mr Griffin did deny saying black people walked like monkeys.

Later, Mr Griffin was also heckled and called a “disgrace” by members of the audience as he said he found homosexuality “creepy”.

Another member of the audience told him: “The feeling of repulsion is mutual.”

Afterwards other members of the audience gave their verdict on Mr Griffin’s performance.

“I think he came across very badly. By the end, the audience were essentially ridiculing him and shouting things at him,” said David Kernohan.

“He was very nervous. I don’t think he would be pleased with the performance.”

But the last word went to Mr Griffin himself. It was after all his night.

Reviewing his own performance he said: “People will see the extraordinary hostility shown to me from the people representing the three old parties. It’s still a matter of the main political parties being against the outsider and that is what it is about.”