@jobellerina: Whilst delivering a strategic planning event, a male attendee comes in, walks past the young male intern, and hands me his coat

This is a story of a tweet. Not the one above, but the one it was responding to. I did not set out, last Thursday morning, to become a trending topic on Twitter. As usual, I woke early and turned on BBC Radio 3 and listened to presenter Sara Mohr-Pietsch's playlist of women composers and performers to celebrate International Women's Day. This led me to tweet that literature was a more hospitable place for female artists than music or theatre because all you needed was an hour or so alone. A few minutes later, I added another tweet, a summary of an argument I have been posing to young women who say they are not feminists and owe nothing to feminism: for you I'm-not-a-feminists, in 1979 aged 28, when I applied for a store credit card the form had to be signed by my husband or father.

This incident took place in a now-defunct department store in Canada where I was a graduate student, and the male clerk on the other side of the desk witnessed me blow up like a nuclear bomb in his face. When, years later, observing the beginnings of a backlash against feminism, I asked I'm-not-a-feminist women if they were happy to bring back the times when their finances were controlled by male family members they were obviously shocked. Of course not. So who got rid of these requirements? Feminists did, by kicking up a fuss. And so my little contribution to International Women's Day was to remind younger women that the rights they take for granted were achieved by those feminists with whom they feel they have nothing in common, rights which did not always exist, even in their own lifetimes.

I closed down Twitter, got dressed and began work. A couple of hours later, I checked on Twitter again, and found that my observation had been retweeted many times. My feed was filling up with observations from other women about their own experiences of sexism past, the casual, low-level, everyday sexism of women treated as second-class citizens by men. The first I noticed was from @ Rosebudlia, who wrote: Earlier than that I wanted a washing machine and I had to sign that my husband or male figure would guarantee my payments. @Carissa_Mason noted: I know a woman who, just 40-45 years ago, was required to have a man provide consent for her emergency caesarean! @harrietvde said: My mum was a 39-year-old well respected journalist on a national newspaper when she married my father and was forced to quit. From @JuliaHines: A consultant who was teaching a seminar of me & 5 other med students apologised that he had not realised he was teaching nurses.

I thought I might as well retweet a few of them, and I went back to work. An hour later my iPad and iPhone were continuously pinging from another room with notifications from Twitter of new mentions. By lunchtime, my entire timeline was inundated with tweets from women who both recognised the world I had been describing and wanted to add their experiences of life before feminism, but many were describing contemporary incidents: @beckyfincham: In 2002,after uni I worked for a recruiter in Folkestone where I "had to wear a skirt" as boss didn't "like women in trousers". @surreyspinster: Assistant at a major electrical shop asked if I wanted to consult my husband before making such a big purchase. @actual_vortex: I teach exercise science and male students will often check with my male colleagues that I'm right. I'm the senior tutor!

I decided to stop work and focus on retweeting the floods of responses. Some of my mentions were alerting others to look at my timeline; many expressed shock and rage at what they were reading. I realised I was curating, in real time, the on-going collective experience of the ways in which some men have tried to diminish women's importance or deny us control over our own lives. One theme came up over and over again, that financial institutions have still not caught up. Numerous tweets referred to female joint mortgage or bank account holders being told that the institution would only speak to the man on the account, and of letters sent to the male signatory only. The Guardian's Deborah Orr, wife of the novelist Will Self, tweeted: Ten years ago Broker insisted on phone that he had to speak to Mr Self about our joint mortgage, not me. I moved our business.

Male responses to the tweets fell into four categories. First, inevitably, the sexist banter (bet you wish your hubby had had to sign when you got your bill for your shopping spree ha ha). Some men tweeted me that they were cringing in shame at what they were reading; others dismissed my original tweet about the credit card application as an example of long ago, completely missing the point that the intention was to demonstrate that women's equality has not always existed like grass and trees and had to be fought for. Others asked when was there going to be an International Men's Day? There is one, it's November 19, feel free to raise your own hell on it.

In the evening I went to a concert at the Wigmore Hall. I tried to keep up with the retweets while waiting for it to start, and in the interval. When I got home, someone pointed out that there were up to 2,000 contributions to my timeline (and I'd gained 800 followers). Now, many of the tweets coming to me were responses to the timeline: @cairnage: The stuff @lindasgrant is RTing now is making me shake with fury. Some began to suggest that there should be a permanent record of the tweets, before Twitter sent them into timeline oblivion. A male Irish software engineer and writer, Paraic O'Donnell, whom I have never met, only discussed chamber music with online, very kindly offered to build a permanent home for the tweets, which goes live today. Selecting the most relevant ones, he suggested calling it A Thousand Reasons. A thousand reasons why feminism is still relevant and necessary.

Feminism has been the greatest and most successful revolution of my lifetime, the single most significant achievement of my generation of babyboomers. It has altered women's lives beyond all recognition. Young women today have little or no idea of what it was like to have to seek permission from a father or husband to sign papers, get a loan or a mortgage, to be forced out of your job when you married or had children, to be denied contraception because you were single, to be thwarted in ambition. A story I wrote for the Guardian in the mid-90s revealed that girls routinely scored higher grades than boys in the 11-plus, but as there were an equal number of places for boys and girls, boys were passing with lower marks than girls consigned to the secondary moderns. Until 1974, there were only five colleges offering places to women compared with 27 for men, and some employers only recruited from Oxbridge wanting "the best and the brightest". I remember being told that the best way for a woman to become a producer at the BBC was to enter as a secretary and get promoted. What, I wondered, were men advised?

Much of the struggle for women's rights today is taking place in countries where girls are denied the right to go to school at all, where their bodies are being mutilated by clitoridectomy and their lives stunted by forced marriage. Worse things happen to women every day including rape and domestic violence, than being snubbed or ignored. These horrors indicate the continuing vast inequality between the sexes. No, it's not the worst thing in the world, but that doesn't mean you can pretend it's not happening. I hope that athousandreasons.com will serve as a free resource for students, academics, teenagers, mothers and fathers, to examine everyday experience, not rhetoric or theory, but the very air we breathe, the way we live, yesterday and today: the small indignities, the opportunities denied, the insults, the patronage, the dismissal, the ignoring, the diminishing, the low expectations, the whole indignity of sexism, including the relentless jokes about it, jokes that are rarely made in relation to racism.

And waking up to it all, and thinking, as you look down at the application form where your husband or father is supposed to give you permission to spend the money you have earned, "I'm not putting up with this." And I don't care if some people think feminism is a dirty word, because without it, we'd still be back where we were, stuck forever, too scared to open our mouths in case men think we're not feminine enough. Enough of cupcakes and high heels, they have their place, but they didn't win me the right to buy them.