When Khan, a former chair of the Fabian Society, resumed his speech he quipped: "On the plus side, I wasn't served with a P45" - a reference to Theresa May's Tory conference speech that was interrupted by a prankster.
Kassam remarked on the campaign against Trump by the political figures ahead of his anticipated visit: "Sadiq Khan as the mayor of London has really been tubthumping, trying to get President Trump not to attend".
Pro-Trump protesters stormed Sadiq Khan's speech at the Fabian Society to try and make a "peaceful citizen's arrest" on the Mayor of London.
One protester announced they were there to perform a citizen's arrest of the London mayor.
Mayor of London Sadiq Khan during the opening ceremony of the World Athletic Championships.
Audience members began to heckle and slow-clap, and security guards entered the auditorium.
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As attempts were made to eject them, one of the protestors could be heard saying: "We stand under Common Law jurisdiction". The protesters were later escorted from the venue by police.
Mr Khan told delegates: "It is a pleasure to be here even though we were distracted by the actions of what some would call very stable geniuses". "We're not leaving, we've paid for a ticket", reported the Evening Standard newspaper.
The protest was seen to be in response to comments made by Khan following Trump's decision to cancel his visit to London next month because he was opposed to the location and price tag of the new USA embassy, which he was set to attend the opening of.
The demonstrator also accused the Fabian Society of "subverting" the constitution.
Mr Trump confirmed on Friday he had cancelled his proposed trip to London.
Last Saturday the U.S. president used the same phrase to describe himself in a tweet following questions about his mental health.