You seem to have a view of the uk legal system that is rather divorced from reality. Both criminal and civil laws are not purely reactive to the committing of an act itself.
You are aware of the concept of conspiracy in English law, for example?
https://www.lawtonslaw.co.uk/resources/conspiracy/
Or the granting of injunctions to prevent things happening?
Both of which require a burden of proof that has not been met.
If it's as lovely and simple as you seem to think it is could you explain why a number of politicians, lawyers and even the mayor of London are challenging the Mets actions?