I agree with jane fae.
Until about five minutes ago, everybody, and I mean everybody, believed that a women-only space was permitted but not required to exclude biological males with the protected characteristic of gender reassignment (irrespective of GRC status), and also that such exclusion could be illegal discrimination (by disadvantaging them relative to non-trans people and relative to the opposite sex - post-Haldane, the comparators differed between GRC-holders and non-holders, but the effect was the same).
There was official guidance about when such trans-exclusion was justified. It had to be a proportionate means to a legitimate end. Stonewall said 'this is a high bar; it virtually never applies'. That's not a lie; it's an opinion.
The SC ruling has changed everything, not just by what it had to say about certificate sex, but with its observations about the operation of the single-sex exceptions under Section 158 and Schedules 3 and 16, and nobody saw it coming.
Anyone who disagrees, point me to anything on this board or elsewhere, in the three years post-Haldane, that argues, eg:
"David Lloyd gyms' changing rooms purport to be women-only, and that means they must exclude all transgender women without a GRC in order to benefit from the exception from sex-discrimination law provided by Schedule 3"
Nobody argued that, did they? We were all "mixed-sex changing rooms are discrimination against the more vulnerable sex" (also a valid argument).
SC changed everything, the clever, clever buggers. I am so in awe 😍 🥳