A speech by London Mayor Sadiq Khan has been disrupted by protesters shouting pro-Brexit and Pro-Donald Trump slogans.
Mr Khan's address to a Fabian Society conference in London had to be suspended for several minutes due to the incident.
The demonstrators, from a group called the White Pendragons, were escorted from the venue by police.
Video shared on social media appeared to show the moment the activists interrupted Mr Khan's speech, moments after the mayor was introduced to the stage.
One man could be heard addressing the audience with: "Ladies and gentlemen, we're here today to make a non-violent, peaceful citizen's arrest."
Audience members started to heckle and slow-clap, during which security appeared.
However their attempts to eject those responsible for the disruption were initially met with aversion from the protesters, one of whom could be heard saying: "We stand under Common Law jurisdiction.
"If you touch us, you'll be done for common assault. Please stand back, do not touch us.
"We're not leaving, we've paid for a ticket."
He then accused the Fabian Society of "subverting" the constitution.
When he resumed his speech Mr Khan tried to make light of the incident with a reference to Prime Minister Theresa May's Tory conference speech which was interrupted by a prankster, saying: "On the plus side I wasn't served with a P45."
And in a dig at the US president after Mr Trump described himself as a "very stable genius", Mr Khan said: "It is a pleasure to be here even though we were distracted by the actions of what some would call very stable geniuses."