By Phoebe Cooke
Six female Greenpeace protesters scaling the Shard skyscraper have prompted the closure of the building's popular viewing deck.
A spokesperson said the "extreme danger" faced by the climbers, who began their ascent at 04:20 this morning, had forced the move.
Campaigners plan on unveiling an artwork once they reach the end of their 'ice climb' - a largely symbolic name for the ascent chosen because the protest is an attempt to draw attention to potential drilling by Shell in the Arctic for oil - and because the Shard was designed to resemble an ice shard.
Greenpeace Arctic campaigner Sara Ayech told Politics.co.uk: "We hope that today is a moment where Shell executives look out of their windows, see the extraordinary thing that these women are doing, and are moved by the art work that is unveiled. This is not just six women; this is the work of three million people."
Shell has three of its main offices based in London, all of which will be visible to the protesters once their climb is complete.
Aychen said the actions of companies such as BP and Russian firm Gazprom had set a bad precedent on the world stage for oil drilling, and that Shell looked set to follow – which could have disastrous consequences on this area.
"We've been running a camp for just over a year called 'Save the Arctic' which is about trying to make the area around the north pole a global sanctuary, which would prevent industrial exploitation, such as oil drilling taking place there," she added.
"If they do drill for oil there, we're also very concerned for the unique, fragile and pristine ecosystem, and the unique species that live there.
"If there's an oil spill there, it will be impossible to clear up and will be devastating for the region. There's a one in five chance of a deep water horizon region blowout."
Shell responded to the action today by stating that, whilst it respected the freedom of others to voice their opinions, the drilling of oil was "nothing new".
"The Arctic region currently produces about ten per cent of the world’s oil and 25% of its gas," it said in a statement.
"If responsibly developed, Arctic energy resources can help offset supply constraints and maintain energy security for consumers throughout the world. Shell has been operating in the Arctic and sub-Arctic since the early 20th century, giving us the technical experience and know-how to explore for and produce oil and gas responsibly."
The Shard's official response has changed throughout the course of the day, with the press spokespeople now claiming that the protesters' actions are "extremely dangerous".
"The Shard continues to work with the emergency services and we are in constant discussion with the Greenpeace representatives to ensure the safety of the protesters," its latest press release said.
Greenpeace told Politics.co.uk that the protesters are putting themselves in no more danger than those who clean the Shard every day - and that the campaigners, all experienced climbers, have been in training for several months to take on their climb.