Hundreds of police officers are being drafted in from across England and Wales to help cope with the Extinction Rebellion protests in London.
Demonstrations shutting down the roads around Parliament and Whitehall to call for urgent action on the climate change and wildlife loss have continued into a third day, including mothers with babies marching on Downing Street.
Metropolitan Police Commissioner Cressida Dick said thousands of officers from the London force and colleagues from around the country were working long hours in challenging conditions.
They have managed so far to secure the bridges and clear the arterial routes through London, and thereby minimise disruption.
The National Police Chiefs' Council said 500 officers are being drafted in from across England and Wales, with police being sent from all the 10 regional organised crime units that cover the two countries.
They are arriving in tranches across this week, with officers from forces closest to London such as Kent, Sussex and Hampshire already in the capital and others set to arrive in the coming days.