Around 80 tonnes of equipment used by Extinction Rebellion protesters to set up camps in central London has been seized by police.
Officers are clearing any sites outside the pedestrian area of Trafalgar Square after restrictions were put in place to stop disruption in the capital.
They have seized so much equipment – including tents, portable toilets and generators – that it would fill eight 10-tonne lorries.
Two weeks of protest action by Extinction Rebellion began on Monday, occupying 12 sites in and around Westminster.
Speaking to journalists on Wednesday, Metropolitan Police Deputy Assistant Commissioner Laurence Taylor said six of the sites had already been cleared and more than 600 people arrested – more than half the number detained during similar two-week protest action in April.
Frontline officers across London have been put on a 12-hour shift pattern to allow colleagues to be moved to cover the protests.
Another 500 officers have been brought in from forces across England and Wales as part of the established mutual aid system for major events.
Mr Taylor said: “We’ve got a very robust policing response to the Extinction Rebellion protests.
“The Met is a very large organisation. We will cope. But there is no doubt it is having an impact on our policing operation more widely.
“We’ve brought in a significant number of officers from communities across London to police central London, and they’re officers who should be working in their local neighbourhoods.”
It can take hours to move activists who have trapped themselves with bike locks or glue, and a minimum of four officers is needed to move demonstrators who refuse to stand up when they are arrested.
Mr Taylor said: “This is a really complex policing operation and it takes an awful lot of time to move even a small number of people, let alone the numbers that we are experiencing in London.
“It takes seconds to glue yourself on to something; it can take an hour or more to unglue that person. Where people are locked around their necks with bicycle D-locks, it can take hours to remove those.
“All of this contributes to the length of time it takes us to clear streets.
“We’ve recovered eight 10-tonne lorries’ worth of equipment from the protest groups. That is an enormous amount of property that we’ve seized.”
The protesters are planning to target City Airport on Thursday, but Mr Taylor said: “We have got plans in place should they go and target the airport so that we can intervene and we can deal proactively with anybody with that intention.”
The State Opening of Parliament is also due to take place on Monday.
Asked if the force has any specific plans in place to avoid disruption, Mr Taylor said: “It’s a security operation as well as a public order operation and we have a number of plans in place to ensure that will take place.”
Metropolitan Police Commissioner Cressida Dick warned protesters outside the designated area in Trafalgar Square that they faced arrest and a potential criminal record.
She said: “To the Extinction Rebellion protesters. You have already seen that if you act unlawfully, we will arrest you and we will seize the things that you are using to obstruct the highways in London.
“We’ve arrested more than 600 protesters in the last two days. We will continue to be very positive and deal with unlawful behaviour.
“If you want to protest, you can go to the middle of Trafalgar Square.
“If you are protesting in the other sites, you are acting unlawfully, we will arrest you, I imagine you will go to court and you are very likely to get a criminal record.”