Police have issued a safety warning over a climate protest rally in the southwestern city of Bristol on Friday which will be addressed by teenage activist Greta Thunberg.
Organizers say they expect between 15,000 and 60,000 protesters from across the country to attend.
One coach company said it was providing transport from 13 places around Britain, including Oxford, Birmingham, Brighton and Cardiff.
Police and the local council in Bristol issued a joint statement, expressing safety concerns.
“We have seen a number of protests over the last year however this one will be significantly larger,” it said. “Please do not underestimate the scale of this protest.”
Police will close roads around the area where Thunberg, 17, is expected to speak before she joins a march through the city.
Thunberg has been in Britain since the weekend. On Tuesday she visited the University of Oxford, where she met Malala Yousafzai, the 22-year-old Nobel Peace Prize winner and campaigner for girls’ education, who is studying there.