Protesters posed 'serious threat'

Officers said some of the protesters have links to climate change groups, but would not name any organisations.
Over 200 officers from five forces were involved in the operation at the Iona School in Sneinton.
A Nottinghamshire Police spokesman said the group were believed to be targeting the Ratcliffe-On-Soar coal-fired plant.
He added: "Information received during the operation indicates that a number of those arrested may be linked to a group of climate change protesters who have set up climate camps.
"This group have previously staged demonstrations at Drax power station in North Yorkshire, Heathrow Airport and Kingsnorth power station in Kent."
'Great news'
The plant at Ratcliffe-On-Soar, which is run by the energy company Eon, has seen protests by environmental campaigners in the past, including members of Eastside Climate Action.
However, speaking on behalf of the group, Bob Andrews said: "We don't know anything about the arrests...