Thomas the Tank Engine Wikia
Thomas the Tank Engine Wikia

Class 40, also known as The Diesel, D4711 (in the Railway Series), D261 (in the television series) or simply Diesel is a diesel engine who once visited the North Western Railway on loan from British Railways.


Class 40 was built at the Vulcan Foundry in Newton-le-Willows, Lancashire, England. Class 40 was sent to Sodor in 1962 to assist the engines with goods and express work towards the end of Stepney's visit, but he only insulted the other engines by saying they were out-of-date, should be scrapped and bragged about his modernity. He got his comeuppance when an inspector's bowler hat jammed his air intake, causing him to break down and to become as sick as boiler sludge. He sulked in the shed while Duck and Stepney took the Express for him to Cronk (Crovan's Gate in the television series).

While everyone was fare-welling Stepney, a disgraced Class 40 crept away, leaving behind "a rather nasty smell of bad manners and a battered bowler hat".


Class 40 is snobbish and rude, believing that diesel engines are superior and should take over from steam engines. Despite this, in the magazine stories, there are some occasions in which the Diesel is polite and helps out the steam engines.

Technical Details


Class 40 is based on a British Rail (BR) Class 40 1Co-Co1. Diesel 40125 and Diesel 782 are also members of this class. 200 members of this class was built from 1958 to 1962, and the last was withdrawn in 1985. They where given the nickname "Whistlers" because of the strange whistling noise their engines would make. Seven Class 40s are preserved with the first built, D200, at the National Railway Museum.

Class 40's television series number belonged to a real Class 40. The real D261 entered service on the 26th of February 1960 and in 1973. It was repainted into the BR Rail Blue livery and renumbered to 40 061 until the engine was withdrawn from service in 1983 and scrapped at Crewe in March the following year.


Class 40 is painted in the BR two-tone green livery. He has yellow warning panels on his front and back end. His rooftop is painted grey. In the television series, Class 40 is painted in the BR Brunswick green livery. He has a thin, lighter green stripe running along his top and yellow warning panels on his front and back end. His number is painted on his cab sides in yellow.

In The Railway Series, his face was yellow, while in the television series, it was grey like the other engines.


Audio Files


First used Last used Sound Effect
Series 4 Series 4


  • Class 40's Railway Series livery is slightly inaccurate as none of the Class 40 diesels received British Railways two-tone green livery.
  • Class 40 is called "Diesel 261" in Japan.
  • According to some VHS descriptions for the fourth series episode Bowled Out, Class 40 was brought to Sodor to take over Daisy's work while she was ill.
  • Class 40's nameboard sequence has only appeared in Cranky Bugs and Other Thomas Stories and in the airings of Bowled Out in Japan.
  • In the magazine story Platform Picture, he is referred to as "Derek the Diesel".
  • His Hornby model depicts him as a Class 37 diesel which still has an inaccurate number for a locomotive of this type.
  • His Railway Series number is completely fictional, as no diesel engine ever is known to have worn this number.
  • In the Days Out with Thomas events, Class 40 wore Toad's face.
  • Class 40's television series model is currently on display at Drayton Manor Theme Park and is wearing his sad face.
  • Series 10 production notes incorrectly call him "Diesel 140". Series 12 production notes call him "Diesel 40".
  • Class 40's Take 'n' Play model incorrectly depicts him with a Bo-Bo wheel arrangement. This was likely due to the fact that the manufacturers could not depict him with his correct 1Co-Co1 arrangement.
  • His horn sound was reused for Mavis in the fourth series episode, Thomas and the Special Letter.
  • Class 40 had a total of six facial expressions, one of which (a cross face) was never shown on-screen. However, his happy face is only on his face references from the fourth series, but not on his face references from the sixth and twelfth series. It is possible that his happy face was either lost or destroyed during or after filming of Thomas and the Magic Railroad.
  • His engine sound is shared with BoCo from the fourth-fifth series, as well as Rusty, but only in the fourth series episode, "Rusty to the Rescue".



* RWS only | ** T&F only