The toppling by anti-racism protesters of a statue of a slave trader in the English port city of Bristol has given new urgency to a debate about how Britain should confront some of the darkest chapters of its history.

The statue of Edward Colston, who made a fortune in the 17th century from trading in West African slaves, was torn down and thrown into Bristol harbour on Sunday by a group of demonstrators taking part in a worldwide wave of protests.

Statues of figures from Britain's imperialist past have in recent years become the subject of controversies between those who argue that such monuments merely reflect history and those who say they glorify racism.

By taking matters into their own hands, the protesters raised the temperature of a debate that had previously remained confined to the realms of marches, petitions and newspaper columns.

Prime Minister Boris Johnson's spokesman said the removal of the statue was a criminal act.

"The PM fully understands the strength of feeling on this issue. But in this country where there is strong feeling, we have democratic processes which can resolve these matters," the spokesman said.

But others countered that such processes had failed to recognise the pain caused by the legacy of slavery.

"People who say - authorities should take statues down after discussion. Yes. But it isn't happening. Bristol's been debating Edward Colston for years and wasn't getting anywhere," said historian and broadcaster Kate Williams on Twitter.

Protesters throw the statue of Edward Colston into the water beside Pero's Bridge, during a protest against racial inequality in Bristol, Britain June 7, 2020 in this screen grab obtained from a social media video. Twitter/Sellottie /via REUTERS

"Personal affront"

A street and several buildings in the city are still named after Colston, and the plinth where the statue stood bears the original inscription from 1895, which praises Colston as "virtuous and wise".

The mayor of Bristol, Marvin Rees, said he did not support social disorder, but the community was navigating complex issues that had no binary solutions.

"I would never pretend that the statue of a slaver in the middle of Bristol, the city in which I grew up, and someone who may well have owned one of my ancestors, was anything other than a personal affront to me," said Rees, who has Jamaican roots.

Bristol police said they made a tactical decision not to intervene because that could have caused worse disorder.

"Whilst I am disappointed that people would damage one of our statues, I do understand why it's happened, it's very symbolic," said police chief Andy Bennett.

Even Britain's wartime hero, Winston Churchill, was under renewed scrutiny: a statue of him on Parliament Square in London was sprayed on Sunday with graffiti that read "Churchill was a racist".

Churchill expressed racist and anti-Semitic views and critics blame him for denying food to India during the 1943 famine which killed more than two million people. Some Britons have long felt that the darker sides of his legacy should be given greater prominence.

These debates in Britain echo controversies in the United States, often focused on statues of confederate generals from the Civil War, and in South Africa, where Cape Town University removed a statue of British colonialist Cecil Rhodes in 2015.