Extinction Rebellion activists who staged protests across the capital cost police an extra £7 million and put a "huge strain" on the force, the Met Police chief said.
The activists brought parts of London to a standstill, blocking Waterloo Bridge, Oxford Circus, staging a "die-in" at the Natural History Museum and gluing themselves to trains and even Jeremy Corbyn's home.
Met Police Commissioner Cressida Dick revealed the extra costs of policing the event ran to more than £7 million, which included paying for overtime and kit, such as a cherry picker and barriers.
Ms Dick said: “It put a huge strain on my officers and I cannot speak highly enough of what they gave.
“The guys and girls on the street, many of them were working 12-hour shifts.
“Many of them, they literally did not see their children for days and days. They just got on with it and I am extremely grateful to all of them for what they did, the professionalism and restraint they showed throughout that set of operations.”
Britain's most senior officer said the figure did not include the impact of taking officers away from other work fighting crime in the capital
More than 1,100 people were arrested during the protests which started on April 15 and lasted two weeks.
Some 10,000 police officers were deployed as the protesters demonstrated at key London landmarks.