How Alstom builds a 187-tonne, five-carriage electric train on their 84-acre site in Derby. How the train's aluminium is made at the UK's last remaining smelter in Scotland. How tunnel boring machines are digging ten miles through the hills for the new HS2 line. The history of the UK’s first electric train - Brighton's seafront tourist train, still used today - and how that technology went on to be used in underground transportation all over the world.