About 600 people formed a "human wall" to protest against the feared impact of a power project on a popular Suffolk beach.
Campaigners joined hands and waved flags on Sizewell beach to make the wall, which stretched to around half a mile long, to highlight the impact of planned sea defences.
Energy company EDF has proposed hard defences to protect the new Sizewell C nuclear power station if it gets the green light.
A spokeswoman for the firm said: "Sizewell beach will remain accessible to the public during construction of the power station, apart from very short term access restrictions which will only be in place for safety reasons as we build the beach landing facilities and sea defences.
"This infrastructure will enable us to deliver more equipment and materials by sea, thereby keeping more lorries off Suffolk roads.
"The sea defences for Sizewell C will be landscaped just as they were for Sizewell B, which now forms part of the much loved beach landscaping.
But campaigners say the changes would affect a "nationally important" stretch of shore, which is currently enjoyed by families, dog walkers and joggers.
The event, which was co-organised by Stop Sizewell C, Together Against Sizewell C and Suffolk Coastal Friends of the Earth, had the support from celebrities such as Chris Packham, Emma Freud, Bill Turnbull and Anthony Horowitz.
Pete Wilkinson, from Together Against Sizewell C, said he believes the protest was only "the tip of the iceberg" for the level of opposition to the project.
"The line of people went right up the beach to the northern end and it looked absolutely stunning," he said.
"Yellow flags were flying and the line of people was half a mile long. It was brilliant.
"We've been working through Covid for two years on this and before that, we've been working for a decade on trying to stop this thing.
"Today was the first time we've had a chance to get together, talk to people whose email addresses we might have but nothing else and people have got together at what's been a fantastic event.
"I believe this is the tip of the iceberg for the level of opposition there is in the county to Sizewell C.
"People have gradually got to understand what it's going to mean for this county and I think the people who were here represents probably 500,000 people in the county who are actually opposed to it."
Alison Downes, of Stop Sizewell C, said it was "incredibly moving" to see the amount of people who turned up at the protest.
"It was major commitment for people, and the amount of people who came and gave up their morning was just incredible.
"I think also we've had long periods of lockdown and this is one of the first opportunities people have had to come together.
"To see that line of people, waving flags and some of them holding hands, was just incredibly moving.
"It brought home to me that's it's a movement, this opposition to Sizewell C, and people are united in their feelings about the project.
"We didn't know how many people were going to turn up so this coming together, literally standing shoulder to shoulder on Sizewell beach, bearing witness to the destruction the project would cause to this much-loved area was just incredibly heart-warming to see."
A spokeswoman for EDF added: "Sizewell C will avoid millions of tonnes of CO2 each year and provide thousands of local jobs.
"We will look after the environment while we build the power station and our long-term plans will lead to a net gain in biodiversity.
"While the defences will extend further out than Sizewell B’s, they will not encroach on the heritage coast footpath.
"During construction and operation, members of the public will be able to continue to enjoy Sizewell beach."
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