[graemep]

The UK case involved him being "lead away" by police and "detained" when he returned and spoke so not really an arrest for holding up a blank piece of paper. Not good by any means, but not quite "for holding up a blank piece of paper". The other UK case was about a threat of arrest if he wrote on the paper - that is under the law that bans protests in Parliament Square. Again, not good, but not for holding up a blank piece of paper.

[dgellow]

I thought detainment was a lighter kind of arrest. Seems that I’m wrong and they are distinct concepts (I’m not too familiar with the English terminology here, my bad)

[skeledrew]

When someone is detained, they're just a person of interest wanted for questioning. When they're arrested, it's because they've actually been charged for something.