The Big City Engine is a smug engine who visited the Big Station when he was bringing passengers to the other side of the Island.
- The prototype Big City Engine features a different face, more detailed wheel arches, an additional wheel arch near the front, wheels slightly apart from each other, and incomplete boiler stripes.
- Big City Engine's name is sourced from the character's London heritage. His actual name is unknown, as he has only been referred to as "the foreign engine" in The Railway Series.
- Big City Engine's tender is never seen in his Railway Series appearance. He is based on a LMS Patriot but is given a custom tender design, with an acronym of his name on the side, instead of a proper British Railways crest or the LMS logo.
- Big City Engine has green wheels despite having grey wheels in his Railway Series appearance.
- He is the only engine to receive counterweights on his wheels.