Fourteen years to design and build and costing around a billion pounds, nuclear submarine the Astute is one of the most technologically advanced and controversial machines in the world.
For over a year the BBC filmed its construction inside one of the most secure and secret places in the country. The film features many of the workers including Erin Browne, a 19-year-old apprentice electrician who wires up the boat; Commander Paul Knight, responsible for the safety of the nuclear reactor; and Derek Parker, whose job involves moving massive pieces of the submarine that weigh hundreds of tons into position before the welding team join them together.
Computer graphics go inside the construction of the submarine itself, giving a blueprint of the design, the life-support systems and weaponry. They also help to illustrate the areas that could not be filmed due to national security.
The story takes a dramatic turn when an unforeseen event means the submarine has to sail into the open sea for the first time during one of the wettest and windiest weekends of the year.