Just Stop Oil activists have refused to rule out targeting Sunday’s London Marathon, following their disruption of the World Snooker Championships earlier this week.

Some 50,000 demonstrators are expected to gather around Westminster from today until Monday to demand an end to fossil fuels, according to Extinction Rebellion, which is organising the event.

It is bringing together more than 200 environmental, civil society and union groups for what it says will be one of its biggest protests, including Greenpeace, Public and Commercial Services Union, Friends of the Earth and US non-profit Avaaz.

They hope to force the government to stop handing out new fossil fuel licences – a demand that the government has rejected.

Burning fossil fuels is the primary cause of climate change and the associated emissions continue to rise globally in spite of climate agreements, although they are expected to peak around 2025.

Extinction Rebellion has asked its members to help guard the London Marathon from disruption, having in January pledged to stop targeting protests towards the public, which previously involved actions like gluing themselves to a train.

But it said it cannot prevent other groups in the joint protest from doing so.

Just Stop Oil, two members of which this week spread dye across a snooker table at the Crucible Theatre in Sheffield, declined to give such reassurances.

“We never rule out anything,” said spokesperson and protester James Skeet.

He told Sky News: “Just Stop Oil will do whatever is non-violently necessary to draw attention to the crisis, so we wouldn’t necessarily rule anything out within that framework.”

But he said the nature of their protests, which usually require an element of surprise, and are in a “grey area” of legality, means they will almost always refuse to say one way or another.

Just Stop Oil said they had met with London Marathon representatives on Wednesday and asked them to “issue a statement in support of our demand to end new oil and gas”.

In a statement they said: “The two parties have agreed to continue to discuss arrangements for the London Marathon, the climate crisis and the need to end new oil and gas.”

This weekend’s event, known as “The Big One”, is organised around a different theme each day.

Friday will see “people’s pickets” outside government departments from 7am until 6pm, to highlight the UK government is “failing” to meet its climate targets.

Although the UK has ambitious climate targets and its emissions are falling, its plans are still insufficient, according to analysts at Climate Action Tracker. Its latest plan, Powering Up Britain, was met with criticism.

Saturday coincides with the global environmental awareness day Earth Day, and will focus on nature and biodiversity. Naturalist and broadcaster Chris Packham and Delia Mattis of Black Lives Matter are due to speak.

Sunday’s protest takes place at the same time as the London Marathon and is themed “Running Out of Time”, to support “causes amplified by the climate crisis”.

An Extinction Rebellion spokesperson said: “It’s our intention to facilitate the marathon to take place smoothly.”

They added: “Everyone is committed not to disrupt the race, and our stewards who are responsible for the whole group will facilitate that.”

The “peoples pickets” will return on Monday, aimed at MPs. A march to “end fossil fuels” will go from Parliament Square to Jubilee Gardens.

Monday also brings the deadline by which the campaigners want the government to respond to two demands, issued this week. If not, they have threatened to escalate their campaigns “in new and inventive ways”.

They want ministers to end new fossil fuel licensing and to create “emergency citizens’ assemblies” to give people a say on solutions to “the most urgent issues of our time”.

The government has said demands “issued in this way” will “not be tolerated”.

“These protestors fail to recognise our world-leading efforts towards achieving net zero, including cutting our emissions by 48%,” a spokesperson for the Department for Energy Security and Net Zero said earlier this week.

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