SO this is it. There’s just a few hours to go before the Gender Recognition Act becomes law and there’s a crowd outside the Scottish Parliament singing and chanting and cheering and jeering and I’m right in the middle of it – the banners and placards and angry faces – wondering how we got here and what happens next. I’m worried, I have to say.

I speak to a few of the 1000 or so people who’ve come along: mostly women, all of them concerned about the unintended consequences of the law that will make it easier for trans people to legally change their gender. The placards make their message clear. “Women’s rights are not hateful”. “Save our single sex spaces”. Every now and again, someone mentions Nicola Sturgeon. Boo.

I get talking to a woman who’s holding a banner emblazoned with the words “women won’t wheesht” who says that, as a mother who breastfed her children and later had breast cancer, she’s worried about the risk the changes to attitudes and law on gender pose to language (“chest feeding” for “breast feeding”). Interestingly, one of her own relatives is a trans woman. The conversations have been “tricky”, she says.

I also talk to a lecturer who organised the recent screening in Edinburgh of the documentary Adult Human Female which had to be called off after protests by trans activists, and a nice lady who’d never been on a protest in her life until she heard about the gender law, and the MSP Stephen Kerr who’s left the chamber to show his support. And I talk to a 20-year-old trans woman who appears to be the only one who’s turned up from the other side of the argument. She tells me the new law is progress.

All of them, pretty much, know the law will pass very soon in the building behind us, so in a way we’re already into slightly different territory. Either the supporters of the bill will be proved right and trans rights will be advanced without undermining women’s rights, or the protesters will be proved right and predatory men will seek to abuse the new law and enter single sex spaces. The point is: we don’t know.

Some of the women at the rally tell me what they fear is going to happen next. One says she’s worried about the next ideology that might come along. “It could be even worse,” she says, “and we’ve lost the space to disagree respectfully.” Another tells me she thinks sex being changed on people’s NHS records could mean patients not getting the treatment they need when they need it.

We have no way of knowing yet whether these women are right but what worries me, as an early supporter of the bill who has, I hope, become increasingly open minded to its critics, is whether the Scottish Government is thinking properly about the next stage. Whether you like a law or not, there should and must be mechanisms in place for assessing its effectiveness and impact. What you must never do is pass a law and walk away.

I have to say I’m not confident the Scottish Government gets this. In one of my conversations at the rally, I pointed out that countries such as Denmark and Ireland already have gender self-identification without any of the terrible abuse that’s been predicted. But the protester I was talking to argued that it’s been hard to collect data in these countries because sex and gender have been conflated. In other words, we may not really know what’s happening.

This is surely a not unreasonable point and it strikes me, as someone sympathetic to the legislation, that the least the Scottish Government can do is ensure that we properly assess how the Gender Recognition Act is working in practice. This government has a record of poorly prepared and executed laws which do not reflect reality or expert opinion: the anti-sectarian football laws, the named person scheme, the plans to abolish the not-proven verdict and on and on. They’re rubbish laws poorly done and we don’t want to repeat the mistake with something as important as trans rights and women’s rights.

Thankfully, there’s still a chance to avoid this happening with the Gender Act. What mechanisms are in place to monitor the working of the law? Will there be a review after one year, five years, ten? However supportive you are of the legislation, there is clearly a risk of some kind of someone at some point seeking to exploit it. One of the women at the rally told me of her concern that “something horrible” will happen in a changing room or a single sex space. I have no way of knowing if she’s right but the risk is there and a robust, centralised reporting system under an independent monitor, particularly in the justice and prison system, could tell us what’s actually going on in the months and years to come.

It's also clear that the debate or struggle or fight is not over yet on both sides. Several of the women at the rally told me their thoughts were now turning to possible legal challenges. The UK Government also now has a small window of opportunity to block the reform, although the law is complex and the government will surely be thinking about two issues: the consequences for trans and women’s rights in the rest of the UK but also the consequences for the politics of independence. We know the SNP and we know the UK Government: the SNP will exploit the situation and that may give the UK Government pause.

So where are we, and where am I? There was a time when I’d count myself as a pretty hard-core supporter of trans reform, but a succession of encounters, with trans people and opponents of the reform, has led me to a place I didn’t expect to get to: I’m not sure and I think that’s good. I also found myself in the strange situation last week of standing in the middle of a rally outside Holyrood nodding along to something Joanna Cherry was saying. When you have a conflict of rights, she said, you look at the evidence and work out a way forward that protects everybody.

Ms Cherry is surely right on that and the passing of the Gender Recognition Act could, and should, be the beginning, not the end, of that process. Spend the afternoon, like I just did, with hundreds of people telling you that single sex spaces are at risk and women’s rights are threatened and it affects you. Equally, I’ve spoken to trans people who’ve told me about their struggles, mentally, physically and emotionally. It’s a conflict, it’s uncertain, we don’t know what will happen next, so what we must do now is, calmly, robustly and fairly, gather the evidence.