Protest laws generally revolve around the right to peacefully assemble. If the stated intention of your 'protest' is to block traffic and cause gridlock then that falls to meet the definition of 'peaceful', as it puts public safety at risk.

One of the linked articles quotes the Essex police who mention that one of the people impacted was a pregnant woman in medical distress, unable to receive medical care due to the actions of these 'protestors'. I would imagine there were dozens of similar incidents over the 37 hours they held the city hostage.