By the time the report was released, local British media reported that protests against US President Donald Trump were ongoing.
Police were preparing for an important operation that was expected to attract as many as 50 protest groups.
The Trump Union was planning to march into Congress Square before a gathering at Portland Place in Marylebone at 2pm.
The rally was scheduled to take place in London from 5pm.
More than 1,600 officers were deployed on London streets, including 500 support from other units, Metropolitan Police said.
The US president will not visit Congress as the House is on break for party meeting season, the media said.
According to standards, campaigners demonstrate what is called “the government’s choice to honor those who violate human rights in the United States and around the world.”
Conditions of the Public Order Act are imposed to “prevent serious disruption to the community,” and planned gatherings must close by 7pm, Scotland Yard said.
MNA