Clashes broke out between mourners and London police on Saturday during a memorial for murdered woman Sarah Everard, who went missing as she walked home alone at night.
The 33-year-old's disappearance earlier this month sparked widespread outrage across Britain over police and society's failure to tackle the issue of women's safety.
Earlier on Saturday, the police officer that had been charged with her kidnap and murder appeared in court.
By nightfall more than a thousand people, mostly women, defied social distancing rules and gathered in Clapham Common, where Everard was last seen alive.
Some came to pay their respects.
Others, to protest the lack of security they've felt when out alone.
Crowds chanted "shame on you" at police who were present.
Witnesses told Reuters they saw police drag some women away.
Metropolitian Police Assistant Commissioner Helen Ball confirmed that several people had been detained.
"Regrettably, a small minority of people began chanting at officers pushing and throwing items. Four arrests have been made for public order offences and breaches of the health protection regulations."
Several official vigils had been planned but cancelled due to gathering restrictions.
England is currently under a national lockdown.
People cannot leave their homes without a reasonable excuse, or be outside with more than one person.