I was both shocked and delighted when I read that at the Women of the World festival earlier this month, Queen Camilla held up two stones that had been hurled at the windows of Buckingham Palace in May 1914. The stones had been thrown by two women, and each carried a message on which the justification for their action was written. One of these messages was “Constitutional methods being ignored drive us to window smashing”; another was: “If a constitutional deputation is refused, we must present a stone message.”

The stones broke through the glass and probably landed on the carpet inside the palace. Rather than throwing them away, as we might have expected, King George V and Queen Mary instead seem to have chosen to keep at least two of the stones, perhaps as souvenirs or mementoes, which is how Camilla came to share them with us when she paid tribute to the women behind the protest. It was a brave move that ran the risk of criticism from conservatives and misogynists. Camilla spoke of the suffragettes’ ambition to “make this world a better place for women”. I don’t remember any other royal endorsing the actions of the women’s movement, especially one as provocative, controversial and risky as the Women’s Social and Political Union, which led the campaign for suffrage.

That same month in 1914, a crowd of suffragettes tried to enter the palace to present a petition demanding votes for women to the king. The monarch had already refused to meet the women. But they just turned up anyway: they were the kind of women who did not take no for an answer. Faced with 1,500 police, all armed with truncheons, the protest quickly turned into a riot. Sixty-six women and two men were arrested, and most of those were sentenced to between two weeks and three months in prison.

The suffragettes’ highly organised, courageous protests have inspired activists for more than 100 years. There was the Greenham Common protest in 1981, when women marched from Wales wearing the suffragette colours of purple, white and green and carrying banners to Greenham Common in Berkshire to protest against the presence of American nuclear weapons at the RAF base. Some of the Greenham women were still camping at the gates until 2000 (the base closed in 1992). They frequently chained themselves to the miles of wire that surrounded the base, in a living tribute to the tactics of the suffragettes.

Since then, the suffragettes have been namechecked by protesters, including Climate Rush, Extinction Rebellion and Just Stop Oil. The tactics of these modern protests owe much to the suffrage campaign that stretched from 1903 right up to the first world war. The suffragettes’ tactics were divisive and controversial: their dynamic, direct action campaign – best described by their slogan “Deeds not words” – saw women trying to rush into parliament to take their rightful place. And they were modern, inventing an eye-catching visual brand for their campaign.

They went on marches, got arrested and took personal risks to remind politicians and the press that they wouldn’t stop struggling until the vote was won. Hundreds of women served time in Holloway prison, in London, many of whom went on hunger strike. Those who refused to eat were then subjected to the torture of force-feeding: tied to a chair and tipped back, while a rubber tube was rammed up their nose or down their mouth, through which a liquid substance – usually a mixture of raw egg and milk – would be poured through a funnel into the tube, where it trickled to the back of the throat. In an attempt to prevent the feeding, women struggled; some had their vocal cords damaged, and others gagged and regurgitated the food, which could also easily find its way into their lungs, causing pneumonia for which there were no antibiotics.

One example of the hundreds of stories of suffragette courage I found was in a letter written in 1914 by Dr Charles Rigby about his wife Edith, a militant suffragette from Preston, who was on the run from the police. He had no idea where she was. “It is a difficult business … but for me there is only one course and that is to back Edith. I know her perfect sincerity and love of justice; she feels it to be the only course her conscience allows her to follow. She is willing to suffer blows, loss of friends … and the starvation … she is almost a shadow, scarcely able to stand, with the smile of an angel and the courage of a lion … I do not have the moral courage to do what she has done. I doubt I could do it for any cause. It makes me so ashamed and I feel so unworthy of her.”

We may debate the suffragettes’ methods, but we cannot argue with their effectiveness. Theirs was a single-issue campaign that recruited like-minded women with a laser-sharp focus on a single goal. Sometimes the leadership didn’t have time for democracy; often their tactics took a huge toll on the physical and mental health of the campaigners. But as modern campaigns continue to take inspiration from the suffragettes and their shouty, unladylike methods, we should salute them too: they gave everything to their cause, making extraordinary sacrifices to get women the vote.

• Diane Atkinson is a historian and the author of Rise Up Women!: The Remarkable Lives of the Suffragettes

• Comments on this piece are premoderated to ensure discussion remains on topics raised by the writer. Please be aware there may be a short delay in comments appearing on the site.