Arwel is a cabless black engine who works on the Alun Railway. He was the first engine to work on the railway and, because of this, sees himself as the keystone.
Arwel was built specially by Alun Railway engineers in 1870 when it was decided that a proper locomotive would be required for the ever increasing mining work.
Arwel is quite pompous and can be arrogant at times due to his special features which include cow-catchers and side-plates. However, he has an clear devotion to the Alun Railway and his role in it, and it this which causes him to feel threatened by Bertram's arrival. Having found a lackey in Mighty Mac, Arwel is looked up to by the others for his strength and work ethic.