The Argus, some 250 police, from across the region, were waiting for about 200 protesters.
There were around 20 arrests - mainly of people not doing what they were told - but everyone had been released without charge by this morning.
The whole policing operation, it has been reported, cost about £200,000 - an outrageous waste of time and money in the face of massive Government cuts, and in the face of warnings that over 1,000 jobs are for the chop.
The decision to spend so much money was one taken by the police themselves. But, as ever, it's the protesters who are singled out for blame, for not telling the police of their plans in advance.
This logic is not only naive and a little simplistic, it's vastly counterproductive.
If the police want to reduce costs for future demonstrations, they must take the lead in building trust with the protest movement. Blaming it for the cost of police operations does exactly the opposite.
The reality is peace protesters come in all shapes and sizes - from Christian grannies to balaclava-clad teens: there simply isn't an single individual or even group of people who has the authority or knowledge to tell the police what everyone's going to do.
Even if there was such a group to negotiate with they probably wouldn't do so anyway, yet: there simply isn't the trust there. For too long many peace protesters have viewed the police as likely to arrest them without warning, hold them accountable for the actions of others, and act as a private security outfit for the arms industry.
If we want to reduce costs in future, the police simply must concebntrate on rebuilding trust with the peace movment.
Here's two things they could do right away:
(i) Investigate whether crimes are being, or have been, committed at the factory itself: do the weapons components made there have the correct export licenses? Is enough done to ensure they don't end up in the wrong hands, and aren't ultimately used to commit unlawful violence, or against civilians?
(ii) Stop blaming the protesters! The cost of policing protests and demonstration is a necessary cost of living in a democracy, and if it's costing too much we must decide, as a society, whether to restrict our democtatic rights to take non-violent direct action, or whether to make the police to spend less money on them.
I agree with many of the commentators who have opined that £200,000 is too much money to spend on policing a peace protest. But I blame the police for deciding to spend it in the first place, not those who feel so strongly about the role a Brighton factory seems to be playing in conflict and war that they are prepared to take to the streets.