A man was pinned by police outside of 10 Downing Street, the residence of Prime Minister Boris Johnson on Thursday, as reported by a Reuters photographer.
The man was allegedly holding a St George’s English flag when he was taken down.
There has been no immediate information released by the police but a spokeswoman for Johnson’s office said she was unaware of any protest and did not make any further comments.
This comes on the day which the United Kingdom was due to withdraw on the European Union, now extended until the 31st January 2020.
Hundreds of pro-Brexit campaigners looked to march toward the gates of Downing Street before being stopped by police, seeing a few of the demonstrators detained.
The incident also clashes with trending hashtag on Twitter #brexitriots, jokingly referencing claims by Brendon O'Neiil before the extension that there would be "riots" if the UK does not leave on 31 October.
Conservative Mark Francois also claimed that "Britain would explode" if the UK did not leave, resulting similarly in the BritainHasExploded hashtag.
The Brexit deadline was extended to 31 January after parliament rejected Boris Johnson's Brexit discussion timetable. The extensions resulted in the passing of a motion for a general election which had thrice been blocked on the basis that no deal was still a possibility.