One of the world's largest offshore wind farms has been opened by Prime Minister David Cameron off the east Kent coast.
The London Array has been built in the Thames Estuary - 10 miles north of Ramsgate.
Its backers say the 175 turbines will produce enough electricity to power nearly 500,000 homes.
Mr Cameron said the wind farm was a "big win for Britain" and proved the UK could deliver large-scale projects.
The last turbine was installed in December and the wind farm is now exporting all its power to the national grid.
It has been predicted that the wind farm will lead to a cut in CO2 emissions of more than 900,000 tonnes a year.
'Great place to invest'
Mr Cameron said: "This project has been built by some of the bravest seaman, some of the most talented engineers, some of the hardest workers, and it's going to continue to bring benefits to people in Kent for many, many years to come.
"It's a very big win for Britain. Sometimes people wonder, 'Can we in the West do big projects any more? Can we do the big investments? Isn't that all happening somewhere else in the east and south of our world?'.
"I think this demonstrates Britain is a great place to invest."
The London Array was a joint project between wind farm developers Dong Energy, power and gas firm E.On and renewable energy firm Masdar.
Andy Atkins, who is Friends of the Earth's executive director, said the London Array was an energy scheme Britain could be "proud of".
He said: "The UK has some of the best renewable energy resources in Europe, but ministers aren't doing nearly enough to develop this huge potential and create thousands of new jobs."