An Extinction Rebellion (XR) activist stewarding people near the TCS London Marathon said there were “a handful of naughty people” who would have liked to block the race to protest about the climate situation”.

Up to 50,000 XR activists are in Westminster, central London, for the third day of a protest dubbed “The Big One”, with the race and rally intersecting as runners pass the Houses of Parliament.

The proximity of the two events had sparked fears climate protesters could try to disrupt the annual race.

XR said they would not intentionally do so but direct action protest group Just Stop Oil (JSO) refused to say whether activists might attempt to interrupt it.

"We wish the marathon every success"

Michel, 63, who withheld his last name, lives in Brussels, Belgium, but travelled to central London for Extinction Rebellion’s four-day protest.

Speaking at a barrier to the race route near Parliament on Sunday, he told the PA news agency: “I’m supporting the Extinction Rebellion group and today we are helping the event of the London Marathon as a steward because we would like to stop people from disrupting the race.

“There are a handful of naughty people who would like to block the race to protest about the climate situation.

“We believe a handful of people might want to do an action to block the race to protest that we are not doing anything for the climate and we would like to stop that because we don’t believe it’s necessary.”

London Marathon director Hugh Brasher previously said his talks with XR had prompted the agreement that “they will be uniquely asking all their participants to help guard the London Marathon”.

In a statement, XR member Olly Baines said: “We have worked closely with the London Marathon over six months to make sure that we can safely co-exist during this weekend.

“Yesterday, with the biggest march for nature ever to take place in the UK at the same time as the Mini Marathon, the two events passed peacefully and without incident.”

He said the same arrangement was being repeated on Sunday, adding: “We all want clean air, pure waters and a healthy green planet.

“We wish the marathon every success.”

XR activists, who unfurled a “climate emergency” banner in front of the Winston Churchill statue in Parliament Square, were among the applauding onlookers as marathon runners passed.

By early afternoon, no-one appeared to have attempted to disrupt the race along the famous section of the marathon route.

XR activist Tom Crowther, 22, who cycled from Kent to attend the climate group’s four-day protests, said: “I think a lot of the people who are supporting the marathon probably also support a lot of the values of Extinction Rebellion.”

On speculation that protesters could try to disrupt the race, he said: “I do think it’s quite a desperate situation that we are in globally and I wouldn’t think badly of them (if anyone did disrupt the race).

“But I’m here to support the people who are running.

“I also hope nobody does (disrupt it) but we’ll see, everyone been told not to.”

Marathon event director Mr Brasher had advised people to “watch the marathon from other locations and avoid the Parliament Square area on the day” because it would be busy.

But large crowds of spectators turned up anyway to cheer on runners such as Sir Mo Farah.