Overview: In this bumper Christmas episode, the team are given rare special access to explore the intricate engineering marvel of the Northern line’s Camden Junctions. Built nearly 100 years ago, the junction allows trains to switch between all of the branches of the line and is normally strictly off–limits for access to film. Featuring in-cab footage and a night-time track possession, this is a special tour behind the scenes including a bonus track walk to the nearby disused station, South Kentish Town.