This looks like a human rights challenge to the covid regs which currently do not allow either 'protest' or 'vigil' as a reasonable excuse to leave your home.
The right to protest is included in freedom of assembly (article 11) of the HRA. Our right to protest can be restricted by a public authority if they can show this is lawful, necessary and proportionate in order to protect health (among other things).
So this would take a judicial review to change and we're all familiar by now with how long they take. FPFW's JR against ONS is about as fast as it gets and that case is being expedited because it's an urgent matter of national importance.
If a vigil is planned for Saturday then the whole JR would have to happen tomorrow and that's just not going to happen. For once, I believe the Met - their hands are tied. There's no point challenging the Met, they need to challenge DHSC - Hat Mancock. That's whose signature is on the regs.
It's extremely important that as we come out of lockdown, our human rights are restored fully as soon as possible.
It was shocking to me when 'protest' was removed as a reasonable excuse to leave our homes but I understand why. If it's legal for Piers Corbyn to turn up in central London with several thousand of his deluded mates then there needs to be the necessary resources to make sure that sort of protest meets all the 'covid-secure' rules and there just aren't enough resources for that. I can't see any way of changing the regs that would allow this sensible, socially distanced vigil but not realistically also allow large scale non-socially distanced demos ('I ticked all the boxes on the covid-secure checklist officer, it's not my fault several thousand more than expected turned up, or that they all seem to want to yell and sing and hug each other')
I will support any JR with a realistic chance of restoring our Article 11 rights but this isn't it - not in time for Saturday.
Nevertheless, the regulations allow us to leave our homes and meet with one other person outside of our household, in a public place. It would not surprise me if a large number of women chose to meet one other woman on Clapham Common (close to where Sarah went missing) at sunset (a contemplative time) and it would also not surprise me if many women chose to do this on saturday.