This final episode follows the men and women racing to build London's brand new underground railway - the Elizabeth Line - in time for the first train launch in May 2017. Engineers must construct and fit out a new station at Paddington, erect a 130m-long great glass canopy to soar above the structure and plug directly into Brunel's original grade one listed station - a nerve-wracking feat. At Tottenham Court Road, workers are building underground platforms and concourses the size of an aircraft carrier in the heart of the world's busiest shopping district. The team must carefully remove enormous props that hold apart the station walls, as convoys of concrete trucks drive down Oxford Street where half a million shoppers and tourists visit, every day. In Derby, a father and son team - third and fourth generation train builders - race to construct 66 trains to ferry passengers across the 30 miles of Crossrail line. Every site and engineer must pull together as they race to deliver this new fifteen billion pound railway - one of Europe's largest construction projects - in time for the first trains roll out.