The right-wing extremist activist Tommy Robinson has used the fatal shooting of American right-wing debater Charlie Kirk to mobilize for the demonstration held on Saturday in central London.
The London police Met has 1,600 police officers on duty, of which 500 have been called in from around the country.
TV images from the scene show a massive turnout with tens of thousands of participants, who are to march from Stamford Street south of Waterloo Bridge to Whitehall.
Some concern exists that the event will get out of hand, as at least one counter-demonstration is being held at the same time.
US President Donald Trump's former adviser Steven Bannon is expected to give a speech, as is a representative from the right-wing extremist German AFD, according to The Guardian.
The demonstration is being held under the slogan "Unite the Kingdom" and is described by the organizers as a freedom of speech event. Sky News correspondent describes that what seems to unite the participants is that they are angry, whether it is over "the government, local hotels or the immigration issue".
