I don't know where the GLP v EHRC ruling comes in the hierarchy of significance, but Justice Swift seemed to take the view that 'sex' in workplace regs also means 'biological sex'. He didn't quite add 'duh!' but nearly:
35 ... Short of this, the Claimants’ submission was that having provided a room for women, the 1992 Workplace Regulations do not prevent the employer adopting a policy that the room could be used by both women and trans women. Thus, the submission goes, regulation 20 requires no more than the provision of facilities and says nothing as to the manner in which those facilities should be used. I do not accept this submission. First, it places form over substance, disregarding the obvious purpose of regulations 20 –21 and 24 The obvious albeit unspoken premise of regulation 20 is the provision of private space for each sex for reasons of conventional decency.
[my emphasis]
37 It is clear from this that the objective of regulation 20 is that men and women should use conveniences in separate rooms, not together in the same room.
'Duh!' [my addition]
