Arthur is a tank engine from the London, Midland and Scottish Railway (LMS). He runs his own branch line.
Arthur took great pride in his spotless record, which he soon lost after colliding with Duck's trucks in an incident largely provoked by Thomas. However, this spotless record was soon amended, after Thomas apologised to him for causing the accident.
He was bought to shunt and pull goods, but then was transferred to the coastal run, on which he enjoys working. He is responsible for this line, which is famous for its fish. Arthur, with the exception of Salty (and maybe Porter), is the only engine known to enjoy the smell of fish.
Arthur is a big tank engine who has never been naughty in his life. He was highly esteemed for his "spotless record" before he arrived on Sodor, never having made a mess or a fuss and never having caused an accident. His main duties were to shunt trucks and haul goods trains. Arthur can be a bit naive however and after a jealous Thomas tricked Arthur into setting his standards too high with the trucks, his record did not stay as spotless as he had hoped. Arthur is very obedient, cautious, and well-behaved. He aims to please in his work and do everything as best he can. He now mainly runs the Fishing Route by the coastal village, a duty which Thomas was only all too grateful to be relieved from. Here, Arthur enjoys the sea air and the smell of the fish.
Arthur is based on an LMS Ivatt Class 2MT tank engine developed for the London, Midland and Scottish Railway (hence the initials on his tanks). Unlike his basis, Arthur lacks a sand dome.
According to Robert Gauld-Galliers' original artwork, he was originally going to have the number "41241" painted in yellow on his coal bunker and a top feed like his original basis. The number 41241 comes from a preserved 2MT on the Keighley and Worth Valley Railway, and at one point, 41241 was painted in a maroon livery like Arthur. Three others are also preserved.
Arthur is painted in the LMS maroon livery with gold boiler bands and yellow lining. The letters "LMS" are written on his side tanks in yellow, shadowed by red.