Greta Thunberg joined protesters in London before the Cop26 gathering of world leaders next week.
The young Swedish activist, who has become one of the world's best known climate campaigners, joined a day of action calling for banks to stop their backing of the fossil fuel industry.
She has been confirmed as one of the speakers at the Cop26 Coalition's Global Day for Climate Justice rally next week. Tens of thousands of people are expected to take part in the march in Glasgow on November 6, as the Cop26 environment summit ends its first week.
Ms Thunberg, whose solo school strike in 2018 sparked a movement of young climate protesters, appeared in the heart of London’s financial district on Friday.
The protest began at the Climate Justice Memorial outside the insurance marketplace of Lloyd's of London.
Protesters laid red flowers spelling out “Rise Remember Resist” at the site before beginning their march to several high-profile institutions in the City of London, escorted by police.
Protests were being held on Friday across 26 countries days before world leaders meet in Glasgow on Monday for the Cop26 summit, where global leaders will discuss rising temperatures.
Many environmentalists are calling the gathering, which starts on Sunday, the world's last chance to turn the tide in the battle against climate change.
However, the mood music ahead of the talks seems fairly downbeat, with British Prime Minister Boris Johnson, the summit’s host, saying it is “touch and go” whether there will be a positive outcome.
On Friday, UN Secretary General Antonio Guterres warned at the Group of 20 summit of leading industrial and nations that “there is a serious risk that Glasgow will not deliver.” He said despite updated climate targets by many countries, the world is “still careening towards climate catastrophe.”
In 2015, countries signed the Paris agreement to limit the rise in global temperatures to 1.5°C and reach net-zero emissions by 2050.
The International Energy Agency warns there can be no further exploration of oil and gas after this year.