@NancyDrawed
Thanks for this.
I thought it was great that Prof Winston not only got to state 'I will say this categorically - that you cannot change your sex' but also that prior to that he said 'I'm about to say something that'll probably mean you'll want to edit the programme when I've finished' which I took to be a way of trying to raise the bias and silencing as a huge part of the issue.
However, I do just want to get my head straight on something that he said, which I have heard elsewhere regarding different aspects of sex.
Prof W said 'You have a chromosomal sex, you have genetic sex, you have hormonal sex and psychological - brain sex'
My understanding of the above is that these are all different aspects of the same thing in terms of biology. In other words, you could NOT have a human with XY chromosomes and therefore biologically male, having the hormonal profile (hormonal sex?) of a female? So yes, there is more to being male or female than chromosomes alone, but they are all linked - with the exception of 'psychological brain sex' which I assume is where the born on the wrong body narrative is from. But I have seen it being used as if you could have XY chromosomal sex but XX hormonal sex.
As I understand it (and I am not a biologist, so take all this with a pinch of salt), your last point is where intersex comes in.
So, normally XX = female hormones = female body. And the same but opposite for XY.
But, in rare conditions, something goes wrong. So CAID individuals (like the runner Semenya) are XY. They make male hormones, but their body doesn't respond to those male hormones. So they look superficially female but don't have ovaries or a uterus, and are sterile. At puberty, more hormones are released, which they may respond to somewhat, hence why some of these individuals develop the broad shoulders and increased muscle mass of men.
Semenya has then had her testosterone blocked to (somewhere approaching...) the normal female range. So is someone who has been brought up female, who's pudenda looks female, who is XY with male hormonal levels to which she does not respond, and which have been artificially lowered to female levels.
But, yes, at least 99.99% of the time you can look at someone and be confident of their chromosomal makeup. Just the same way I would bet with reasonable certainty, without even seeing you, that you only have one liver. I might be wrong, but it's vanishingly unlikely. The fact I'm able to name (I did have to google the spelling) an individual where that correlation is broken illustrates its rareness.
What I've never quite grasped is 'psychological-brain sex'. At least, I don't understand whether it's inborn or culturally conditioned. I say that as a woman with a stereotypically male career and interests. I'm also well aware that one of the arguments for denying women the vote was 'their girl brains can't handle it'. So I have an instinctive twitch against the concept of gendered brains. But, if Winston says it, I'm happy to listen.