He eluded anti-racist campaigners protesting outside the council's headquarters in east London by slipping in through a back entrance escorted by police.
Feelings ran high inside the council chamber as Mr Beackon took his seat. An anti-racism campaigner was thrown out after repeatedly disturbing proceedings.
Mr Beackon said: 'The police said as a question of security, would I mind being escorted in. As we are a party of law and order and would always co-operate with the police, I said yes.' He added: 'Next time I will come in through the front door.'
Mr Beackon said he had no intention of speaking at the meeting. 'It is a committee meeting,' he said. 'I have just come along to see how it works.'
BNP officials have been convicted for the first time over racist posters, ending an 18-month court battle by Merton council in south London.
John Tyndall, head of the BNP, and Richard Edmonds, an official of the party, were convicted of illegally displaying posters under regulations governing advertising.
The council won an initial civil action but Tyndall and Edmonds began appeal proceedings which finally ended when Kingston Crown Court ruled in the council's favour and ordered the defendants to pay a fine of pounds 100 and costs.
Tony Colman, the council leader, said: 'We were resolved in our determination to ensure that the BNP could not use their methods in Merton. We do not want to see valuable members of our community intimidated in any way or too frightened to use an area we have developed as their own haven within our community.'Reuse content