A man claiming to be a journalist had to be escorted away by police after disrupting a press conference with Bellingcat founder Eliot Higgins.
Graham Phillips accused Mr Higgins of being a "NATO propagandist" and closed in on him with a handheld video camera.
Conservative MP Bob Seely was in attendance at the event and made an attempt to push Mr Phillips away from Mr Higgins and Bellingcat investigator, Cristo Grozev, who were in the middle of talking to the press about their report on the identity of the second suspect in the Sergei Skripal poisoning.
Mr Phillips continued to disrupt the conference with claims that Bellingcat was "funded by NATO", with the Metropolitan Police eventually escorting him away.
After the event, Mr Higgins posted a link to an article by Buzzfeed profiling Mr Phillips, with the caption "For those wondering who the crazy person was who was screaming at me at our press conference today, here's a detailed profile."
Who is Graham Phillips?
Graham Phillips is escorted away by police. Image: David Mirzoeff/PA Wire
The self-professed "independent journalist" has previously worked for the government-funded channel Russia Today, and Russian TV network Zvezda, run by the Russian Ministry of Defence.
He was born in the UK and has previously lived in the Ukraine.
However, he was banned from the country in 2014 on the grounds of "national security", with the Ukrainian government issuing an open letter to UK authorities in 2016 calling his behaviour towards Ukrainian citizens and members of the military "abhorrent".
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A post written on a blog under the name of Graham Phillips in 2016 explores Eliot Higgins' work and personal life in detail, and he refers to the Bellingcat founder as an "internet joke".
Mr Phillips runs a YouTube channel that currently has 116,656 subscribers, where he posts politically-themed videos, including the footage captured from today's press conference.
His most-watched video is a tank performing tricks in the city of Slavyansk, which has well over one million views.