Climate activist Greta Thunberg was one of those who took part in Friday's action.
She will then travel on to Glasgow.
Greta Thunberg tells the BBC that a "change is possible" during the climate summit, if the pressure on politicians continues.
When asked if she has been asked to speak at the meeting, she says:
- I do not know.
It is very unclear.
Not officially anyway.
During the day, Thunberg also visited the Natural History Museum in London, where she looked at the beetle named after her, Nelloptodes gretae.