You both had a job to do. You knew the state wouldn't - and in fact, couldn't - allow disruption. That you would be arrested preventatively. And that your arrest would be news.
If the purpose of engendering a discussion about change is to create news, then job done.
Arguably the job of the police is not to stop disruption, but lets face it we all know it is. And I don't think people see somebody running in front of a golden carriage or shouting 'Not my King' and think 'oh my god, I've never thought about this before but suddenly a truly representative democracy where Boris Johnson could stand as Sun King in a popular no brain Sun reader vote off seems like an amazing idea'.
But news is news. News creates momentum, the greater the column inches the greater the momentum. Arrest isn't a failure of the system, it is the system. And you are part of it.
We win by presenting an argument that is morally watertight. We saw what populist stunt based victory wrought is these past seven years.