Two men were arrested on suspicion of public order offences during today's demonstration. Hertfordshire Police said:
The men were arrested from within the confines of the trespass banning areas and they are being taken to a police station.
More top news
The shocking video of Laquan McDonald being killed brings the debate about racism in the US criminal justice system centre stage once more.
A video of a white police officer shooting dead a black teenager has been released by authorities in Chicago.
Cold in the wind