An Extinction Rebellion protester has scaled the scaffolding surrounding Big Ben, saying he was inspired by Swedish teen activist Greta Thunberg.
Footage of the stunt circulated on social media showed 43-year-old tree surgeon Ben Atkinson climbing the landmark dressed as Boris Johnson complete with a blond wig, shirt, tie and jacket.
When he reached the top he draped two banners from the structure. One featured the Extinction Rebellion logo on a rainbow background and the words "No pride on a dead planet" and the other said "Citizens Assembly".
One featured the Extinction Rebellion logo on a rainbow background and the words "No pride on a dead planet" and the other said "Citizens Assembly". After reaching the top, Mr Atkinson posted on Facebook: "Gone and done it... Extinction Rebellion. Here to stay."
"We got the declaration of climate emergency last time. Now perhaps, please Boris, you're struggling to navigate Brexit let alone work our way out of the sixth mass extinction event.
"Please. Pretty please.... let's get on with the citizens assembly. Thank's Boris.
"I know somewhere in there you have compassionate feelings towards something other then your career. You've got Premiership. Now you've got a chance to do something that could last for centuries.
"A legacy of being the man that turned it all around. Dare you.
"Oh, and thanks Greta. I heard you calling."
Shortly before climbing the building, Mr Atkinson posted a photo of himself with a blond wig, swimming goggles, blazer and tie, adding: "Ready steady breathe deep... go."
Onlookers said police officers had used a lift that is part of the scaffolding to reach Mr Atkinson and could be seen speaking to him as he sat in the netting.
Other officers were seen at the base of the tower with ropes.
A spokeswoman for the Met Police said the force had officers at the scene, but declined to comment on how they were planning on getting Mr Atkinson down.
Police have closed the entrance to Westminster Tube station that is across the road from Big Ben and are asking people to leave the area directly in front of where the demonstrator is.
Other entrances to the Tube station remain open.
A spokesman for Extinction Rebellion said Mr Atkinson's climb was to highlight Government inaction on the climate and ecological emergency.
It is the latest in a string of stunts staged by Extinction Rebellion on the penultimate day of their autumn uprising - despite being barred from protesting in the capital since Monday by the Met Police.
Earlier the group performed a "red handed" march, where they sprayed hand prints using chalk-based spray paint around Whitehall.
Yesterday, the group was forced to apologise after holding up Jubilee Line trains by climbing on them.
One protester was filmed lashing out at an angry commuter who had pulled him off the roof of a train.