They came from Los Angeles, from Bangkok, from Sydney, from Buenos Aires; from all four corners of the globe. One woman said her plane ticket was a birthday present from her boyfriend, who knew how much it meant to her. Others are funded by student unions, family whip-rounds, expats who have been away too long to take part. Young Irish women and men are coming home to vote in Ireland’s abortion referendum, many wearing their hearts on the sleeves of their repeal jumpers. They swap knowing glances in airports, proudly tweeting and Instagramming as they go. The #HomeToVote phenomenon is an extraordinarily moving, powerful sight. For what cause would you fly halfway round the world and back again? Only one that cuts to the heart of who you are, how you seek to live.

I had to travel abroad to end my doomed pregnancy. Ireland must change its abortion law | Siobhán Donohue Read more

Repealing the eighth amendment would be seismic enough, since it’s what guarantees the unborn a right to life even when the mother has been raped, is practically a child herself, or is carrying a wanted baby with such severe abnormalities it cannot survive. But this referendum has become a public test of so much more; of a woman’s place in society more generally, of a scandal-ridden Catholic church’s moral authority, even of shifting dynamics between the sexes in the #TimesUp era.

Play Video 2:54 My budget flight to get an abortion: the story no one in Ireland wants to tell – video

Some yes campaigners detect small but worrying numbers of men threatening to vote no seemingly from a desire to put empowered women back in their boxes; but also men reluctant to engage, reasoning that this is a “woman’s thing”, even though babies don’t conceive themselves. Since the argument is all about women’s autonomy over their own bodies, perhaps it’s understandable that some men would steer clear. But this battle can’t be won without male votes and the change would benefit men too – at least if they don’t want to see wives and daughters suffer, or indeed to become fathers before they’re ready.

We who watch from abroad – fingers crossed for yes – know we have no right to interfere in Ireland’s decision. We don’t want to presume, yet cannot look away: it’s too visceral. You don’t need to have had an abortion yourself to be profoundly grateful that the right not to give birth against your will exists, a backstop to every other freedom women have. Besides, the Irish vote feels like an omen, a sign of the way the global winds are blowing. Rather like the teen movement for gun control in America, it’s tempting to see the yes movement as part of a millennial blowback against gathering reactionary forces – although older women raised in darker days, when supposedly “fallen” women endured grim punishment in mother and baby homes, are often as anxious for change as their daughters. But there may be more practical implications for Britain too.

Facebook Twitter Pinterest Irish people in London attend a rally for the yes campaign ahead of Ireland’s abortion referendum. Photograph: David Levene/The Guardian

To be clear: a vote for repeal would allow Ireland’s parliament to consider reforming abortion law, but doesn’t guarantee this. The proposals aren’t for no-questions-asked abortion on demand, and they are not, despite what some no campaigners say, wildly more liberal than British law.

But they are different: stricter in some ways (abortion would be legal beyond 12 weeks of pregnancy, and up to 24, only given a risk to the mother’s life, or serious harm to her health), and looser in one. Under the Irish proposals, a woman wouldn’t need to give a reason for seeking a termination before 12 weeks. She’d simply need a doctor to confirm her stage of pregnancy, and then undergo a 72-hour cooling-off period to reflect on the decision. In Britain abortion is legal up to 24 weeks only provided two doctors agree it’s justified on grounds including threat to the mother’s health, or to that of any existing children; serious foetal abnormality; risk to the mother’s life; or grave permanent injury to her.

‘It was the scariest thing I've ever done’: the Irish women forced to travel for abortions Read more

In practice, the law is elastic enough that refusals are rare. But the beginnings of a campaign for abortion on demand at least in early pregnancy are visible in Britain, with campaigners arguing that women don’t make this choice on a whim and shouldn’t have to beg permission. The British Medical Association now backs scrapping the two-doctor rule and bringing abortion under medical regulation, not the criminal law. If the public mood in Ireland has shifted, what about Britain?

Play Video 9:49 Meet the people fighting to keep Ireland's abortion ban – video

Despite being adamantly pro-choice, I’ve always felt ambivalent about further liberalisation. Opening the law up in parliament would let anti-abortion politicians seek their own amendments, a risky venture perhaps when Tory majorities rely on the DUP. The law doesn’t generally stop women ending unwanted pregnancies, but acknowledges concerns, helping ensure public consent.

And since repeated terminations can be a sign of an abusive partner who won’t use contraception or accept a woman’s right to refuse sex, I’d worry that shortening conversations with doctors might reduce opportunities to pick up on victims of domestic violence or sexual exploitation, who may indeed need terminations, but other help besides.

Yet Ireland’s experience makes me wonder if a debate wouldn’t be healthy. There is something exhilarating about the refusal to shove this under the carpet any more, as is the telling of stories once suppressed for shame and fear that have brought greater understanding of women’s lives.

Ireland always told itself it was “banning” abortion when it was only ever outsourcing it; forcing women to bear the burden of unwanted pregnancy alone and silently, pushing them into an online black market in pills or into lonely journeys to clinics overseas. But now the chickens are coming home to roost. Ireland’s young are crossing the ocean in reverse, to be heard. It’s their decision, not mine. But like I said: fingers crossed.

• Gaby Hinsliff is a Guardian columnist