How to build a nuclear submarine
The BBC has been given exclusive behind-the-scenes access as the Royal Navy built its latest nuclear-powered Astute submarines.
The submarines, which cost more than £1bn, take years to design and build, with the first of class taking 14 years to complete. More than a year of the top secret process at one of the most secure places in the country - the BAE Systems shipyard in Cumbria - has been captured on camera.
Weighing 7,000 tons and measuring 100 metres in length, assembling the different sections is a delicate business.
How To Build A Nuclear Submarine will be broadcast on Sunday 27 June at 2100 BST on BBC Two. It will be available for seven days after that on the BBC iPlayer.