Revealed: the darkness behind the beauty of Britain's great houses

Feted for their fine architecture and often used as lavish backdrops for period movies, Britain's great estates came under the spotlight on Tuesday for a darker reason: their links to colonialism or slavery.

The National Trust, which runs some 300 heritage buildings, said about a third of them had past owners who had profited from slavery, opposed its abolition, been involved in colonial expansion or administration or promoted imperialism.

"These histories are sometimes very painful and difficult to consider," it said in a report. "They make us question our assumptions about the past, and yet they can also deepen and enrich our understanding."

The National Trust is a household name in Britain and promotes the properties it manages in England, Wales and Northern Ireland as family days out.

But like other British institutions from Lloyd's of London to Oxford University, the trust was jolted by this year's wave of anti-racism protests into a reckoning with the past that has led to statues being toppled and legacies debated.

The trust said its 115-page report, which was not exhaustive, would be used to ensure that links to colonialism and slavery were properly explained at relevant places.

But the report was met with an instant online backlash because among a list of 93 properties listed was Chartwell, Winston Churchill's home from 1922 until his death in 1965.

Churchill has long been revered as a British national hero for his leadership during World War Two, but his legacy in other areas has come under increasingly critical scrutiny.

The report noted that he had voted against a 1935 India Bill aimed at giving Indians greater autonomy from their colonial rulers, and cited the Bengal Famine of 1943, during which critics say Churchill denied food supplies to India.

Churchill biographer Andrew Roberts was among numerous people who went on social media to accuse the National Trust of "wokery".

"White man's burden"

Another notable item on the list was Glastonbury Tor, a hill topped by a 15th century tower, close to the site of the famous music festival. It was one of 29 properties that had benefitted from a government scheme that compensated slave owners when slavery was abolished in 1833, the report said.

No compensation was paid to former slaves, but 20 million pounds, or about 40 percent of the government's annual expenditure at the time, was set aside for former slave owners. The loan needed to fund the compensation was only fully repaid in 2015.

The imposing Basildon Park mansion, featured in the 2005 film adaptation of Jane Austen's "Pride and Prejudice" starring Keira Knightley and Matthew MacFayden, was also on the list.

It was purchased in 1771 by Francis Sykes, one of the so-called "nabobs", British merchants who made huge fortunes on the Indian subcontinent in ways that would now be considered exploitative.

The list also included Bateman's, home of writer Rudyard Kipling from 1902 until his death in 1936. Kipling, who won the Nobel Prize for Literature in 1907, is known for enduring works of fiction such as "The Jungle Book".

But he was also an influential apologist for imperialism, as epitomised by his poem "The White Man's Burden" which suggested white people had a moral duty to civilise countries inhabited by people of other ethnicities.