LONDON -- It began as a genteel campaign featuring period drama costumes and polite open letters to assure that British bank notes would continue to carry images of women.
It ended up as a fierce national debate over money, power, rape threats and the limits of free speech in the era of social media.
This being Britain, it also featured Jane Austen as a central character.
Three months ago Caroline Criado-Perez, a blogger and co-founder of the Women's Room Web site realized that there might soon be no women, save Queen Elizabeth II, left on British bank notes. Among the five historical figures featured on the notes, only one, the social reformer Elizabeth Fry, was a woman, and she was to be replaced soon by Winston Churchill.
Surely, Ms. Criado-Perez argued, there were enough women of stature in British history to find at least one more?
In case the Bank of England lacked inspiration, she led a group of campaigners dressed up as the suffragist Emmeline Pankhurst, the novelist George Eliot (born Mary Anne Evans) and Boadicea, the Celtic warrior queen who fought Roman invaders in 60 A.D.
Ms. Criado-Perez hand-delivered pages containing more than 35,000 signatures supporting her cause to the bank in the City of London. And she collected £13,000, or nearly $20,000, in donations to mount a legal challenge if the men who ran the bank did not respond to the public campaign or to the 2010 Equality Act obliging public institutions to keep in mind the goal of gender equality in all decision-making.
The departing central bank governor, Mervyn A. King -- fond of pointing out that one woman features on the back of every bill and coin in her kingdom -- appeared to have little time for the debate.
But in July he was succeeded by Mark Carney, a Canadian and the first non-Briton to run the bank in its 319-year history. Mr. Carney seized the opportunity to make a gesture.
Saying that it had always been the bank's intention to include a woman in the line-up of historical characters, he picked an uncontroversial one: from 2017 Austen, the author of "Pride and Prejudice" and "Sense and Sensibility" will replace Charles Darwin on the £10 note. Mr. Carney then vowed to review the whole process of choosing bank note characters.
Ms. Criado-Perez said it was "a brilliant day for women."
But on the same day, harshly negative commentary started appearing on Twitter, a trickle of abuse that at one point grew into a shower of crude and explicit rape threats against Ms. Criado-Perez at a rate of nearly one post a minute. By this week, several other women who had backed her campaign, including at least one member of Parliament, had also been targeted.
"I will rape you tomorrow at 9 P.M.," read one of the few printable threats by a Twitter user with the handle @rapey1, said Stella Creasy, a Labor and Co-operative Party legislator from northeastern London. "Shall we meet near your house?"
A 21-year-old man was arrested and then released on bail. Police officers in the London borough of Camden investigating the abuse against Ms. Criado-Perez said the Twitter attacks appeared to involve several people posting anonymously, or so-called trolls.
What is perhaps most striking about this reaction, said Caitlin Moran, a columnist for The Times of London and author of the 2011 feminist manifesto "How to be a Woman," is how little it took to set it off.
"If even a small thing like this, a nice middle-class debate about putting Jane Austen's picture on the opposite side of a bank note from the queen causes a storm of abuse like this, what will happen when we get to the bigger issues?" she said in a telephone interview.
Herself a frequent target of abuse on Twitter, Ms. Moran is lobbying to make this Sunday a "trolliday" -- a holiday from Twitter trolls -- urging users to boycott Twitter for 24 hours to protest what she perceives as a lack of responsiveness to the cyberharassment.
Twitter has pledged to create a new button to report abusive comments. But the company has come under pressure from 64,000 signers of an online petition to do more, showing how the same technology that exposed people to the abuse has given them tools to combat it.
"It is just as essential that in seeking to enhance our freedoms we do not in fact diminish them," Tanya Gold wrote in a column for The Guardian. She warned against asking social networking sites to "police our debate," suggesting that "misogynists on Twitter should be shamed rather than criminalized."
Mr. Carney and his colleagues at the Bank of England may be relieved to find that the attention of equality campaigners has for now shifted focus away from the still overwhelmingly male world of finance.
If the banknote campaign was about stopping women from being "airbrushed" out of history, in banking history "you don't need an airbrush," said Niall Ferguson, the economic historian and Harvard professor, by e-mail. In the 19th century, female members of the powerful Rothschild banking family were never allowed to look at the books, much less play a part in managing the family firm, he said.
Even today, only 6 percent of today's central bankers are women, according to Mr. Ferguson, and to be sure, as the debate in Washington surges around the candidacy of Janet Yellen to head the Federal Reserve, there has never been a female governor of the Bank of England, nicknamed nevertheless "The Old Lady of Threadneedle Street."
If feminists have been surprised at the force of the reaction, so have employees of the Bank of England, an economist at the bank said on condition of anonymity. The economist was not authorized to speak publicly. Jane Austen was picked precisely because of her broad appeal. She was not a feminist symbol and nobody had foreseen that selecting her would ignite controversy.
"She has a wide popular and a varied political appeal," said Devoney Looser, a professor of English at Arizona State University and an Austen specialist. "Unlike someone like Emmeline Pankhurst, it's more difficult to slot Austen politically. She's embraced by conservatives and progressives both."
This article originally appeared in The New York Times.