Overview:The engineers and builders are about to hit the biggest deadline on the project so far. The tracks which bring the trains into St Pancras must be moved from the east to the west side of the station, over the course of a single weekend. If they fail, the entire £5.8 billion project will be thrown off-schedule. Meanwhile, Chief Architect Alastair Lansley receives some terrifying news that may prevent him from seeing the project through.