Except even if the police had "allowed" the vigil, they'd still have violently arrested women at said vigil. The police don't give a shit about the law.
That's a dumb statement. If the vigils had been legally sanctioned, the police would have stood by and watched as they have done many times before at many protests/marches/vigils. The difference here is that it was explicitly not allowed, and no overriding power to allow them was provided by government. Ergo it's the polices job to stop it.
Obviously the vigil attenders aren't going to walk off and break themselves up because they feel strongly enough about the cause to be there. The police have to do their job. The police aren't in a position here to just decide not to enforce the current laws. Someone higher up the chain should have provided some other guidance, especially considering the Met had mentioned prior multiple times that they would be forced to break up gatherings in regards to this. What's Bojo upto? He could have provided some actual guidance here if he wanted too. It's not like all these facts weren't known.