Workers have fitted a reactor into the first nuclear power station to be built in Britain for 30 years.
Hundreds of engineers and construction staff worked for several days to lift the 500-tonne steel equipment into place at Hinkley Point C, near Bridgwater, Somerset.
"It was a huge operation for all the teams involved," said Matt Abbott, who led the team installing it. "This is the heart of the plant."
The 13m-long (42.6 ft) unit is one of two reactors which will contain the nuclear chain reaction that will generate enough power for six million homes, when it opens in 2030.