Thousands of people rallied in the heart of London on Saturday to support US protests against police brutality.
They waved placards and chanted "No justice, no peace, no racist police."
The rolling global protests reflect rising anger over police treatment of ethnic minorities.
The British government had warned people to stay away because of the threat of the coronavirus.
Huge crowds gathered at Parliament Square - making social distancing impossible.
Later protesters stopped traffic as they marched towards the American Embassy.
British world heavyweight boxing champion Anthony Joshua joined a Black Lives Matter march in his hometown of Watord, north of London.
The fighter walked at the head of the march on crutches following a leg injury sustained during training.