Thousands of supporters of the far-right activist Tommy Robinson have filled Trafalgar Square in central London after a march.
He claimed the event was the “biggest patriotic rally” the UK had ever seen.
A counter-protest by Stand Up To Racism and former Labour leader Jeremy Corbyn’s Peace & Justice Project also took place in London.
The Metropolitan Police said a major operation was in place to “keep the peace” between the two protests, amid fears of serious disruption.
A Trans Pride event was also held in the capital.
Amid a sea of England and Union Jack flags, Tommy Robinson’s supporters listened to speeches attacking immigration and promoting “patriotism”.
He received a loud cheer in Trafalgar Square when he asked the crowd how many of them had voted for Reform at the general election.
He revealed he had asked Nigel Farage to speak at the protest, but said the Reform leader had told him he “couldn’t make it”.
At the anti-racist counter-protest nearby, Jeremy Corbyn gave a speech, and demonstrators held placards reading “no to racism, no to hatred” and chanted “we won’t be silent”.
The Met Police has not said whether the five arrested people were participants in any of Saturday’s protests.
Ahead of the marches, police barricaded Whitehall and mobile units were parked in side streets around Westminster.
One thousand officers were on duty and Scotland Yard used powers under the Public Order Act to place strict conditions on the timing and location of both protests. The Met said officers would remain on duty after the marches had finished.
Chief Superintendent Colin Wingrove, who is in charge of the weekend’s operation, said police would “intervene decisively” to deal with protesters who broke the conditions.
He said: “Our first priority is to keep the peace to ensure that those exercising their right to lawful protest can do so safely.”
Tommy Robinson, whose real name is Stephen Yaxley-Lennon, faces contempt proceedings at the Royal Courts of Justice on Monday after being accused of continuing to talk online about a libel case he lost in 2021.