Climate protesters breached security to enter the site of a coal-fired power station in southeast England today but German firm E.ON, which runs the plant, said output had not been disrupted.
Police arrested eight people at the facility at Kingsnorth in Kent, four who managed to get into the site and four others who tried to access it from an estuary using a raft.
The protesters oppose plans for two new coal units at the facility, which will also be operated by E.ON, and said their aim was to disrupt supply for a day.
"We've had to increase security at the powerstation and members of staff have been worried by what might happen to them," said an E.ON spokesman. "The power station is generating. It's business as usual so much to the extent it can be on this extraordinary day."
The protesters say coal emits unacceptably high levels of carbon dioxide, the gas held responsible for climate change.
"We just want to try and send a message to people that we don't want anymore new coal ... it's something that's not going to help our future at all," said Helen Atkinson (26), a medical photographer from Cumbria.
E.ON argues emissions from the new units will be cleaner and it hopes to bury them underground using so-far commercially unproven carbon capture and storage (CCS) technology.
Protest organisers said about 1,000 people had gathered at a nearby field for a music festival-like "Climate Camp", which has been running workshops on climate change all week.
Since the start of the camp, police have staged a 24-hour security operation involving between 350 and 1,400 officers depending on the day, at a cost of millions of pounds.
Some protesters called the police tactics heavy handed. At one point, protesters clashed with officers who tried to arrest a man after he was seen ripping a police barrier tape.
E.ON, which plans to close the existing plant at Kingsnorth in 2015 and replace it with the new facility, said it was a partner in the world's largest offshore wind farm off the coast of Kent and it was also building one of the world's largest heat and power plants close to Kingsnorth.