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 big green 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goods and express work towards the end of Stepney's visit, but he only insulted the other engines by saying they were out-of-date, should be scrapped and bragged about his modernity.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 after attempting to show off to Duck and Stepney. 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/the nasty smell of bad manners and a battered bowler hat".


Class 40 is snobbish, smug and rude with his snide remarks, believing that diesel engines are superior and should take over from steam engines while also showing off to engines such as Duck and Stepney. In the end however, he would also show his cowardly side as shown when he slipped away after his embarrassing incident when no was looking. Despite this, in the magazine stories, there are some occasions in which the Diesel is polite and helps out the steam engines, even if he was reluctant.

Technical Details


Class 40 is based on a British Rail (BR) Class 40 1Co-Co1. Old Stuck-Up and D782 are also members of this class. 200 members of this class was built from 1958 to 1962, and the last was withdrawn in 1985.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, initially built with the 'disc' headcode marker. In 1965, it along with Nos. D260-D266 would then be converted with the 'central' headcode marker and were based in the Scotland region. Sometime between 1965 and 1970 was repainted into BR rail blue. In 1973 renumbered to 40 061 until the engine was withdrawn from service in 1983 and scrapped at Crewe in March the following year.


In the Railway Series, Class 40 is painted in the BR two-tone green livery, with enclosed yellow warning panels on his front to back end, and his rooftop being 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, full yellow warning panels on his front and back end with his rooftop painted black and shining silver buffers as opposed to the regular grey buffers. His number is painted on his cab sides in yellow similar to the Railway Series illustration.

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


Official Description

From Official Website:[1]

The Diesel: A snooty type of chap. Like all diesels, he thinks he knows it all, which gets up every steam engine's funnel. Despite his immense power, he soon finds out that nothing chuffs like a chuff chuff chuffs!

Historical Note: The Diesel is based on a 2-Co-Co-2 Diesel built by English Electric in 1960, as one of the first production line diesels for main line passenger use. The series of over 200 engines was phased out of service in the 1980’s, though six were retained for freight use in the building of the Channel Tunnel.

From Official Website:[2]

The Diesel: The Diesel is considered to be a little snooty by the other engines because of his "know-it-all" attitude, which "steams up" the steam engines. Despite his immense power, he soon finds out that nothing chuffs like a steam engine.

Fun Fact: The Diesel is based on the 2-Co-Co-2 Diesel engine built by English Electric, as one of the first production line diesels for main line passenger use.

From Official Website:[3]

The Diesel: Like all diesels, The Diesel thinks he knows it all. He thinks all Steamies should be replaced by Diesels. Despite his immense power, he finds out that even diesels need help!

Fun Fact: The Diesel is based on a 2-Co-Co-2 Diesel built by English Electric in 1960.

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's enclosed warning yellow panel in the Railway Series is somewhat inspired/based on one of the actual D261's former 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 incorrectly 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. It also appears his side detailing was incorrectly based on that of a Class 37 diesel much like the Hornby Model.
  • 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".
  • Class 40 and Derek share the same livery.
  • Interestingly, a few of his face mask were based/inspired from the Illustration from Stepney the "Bluebell" Engine, most notable being his Sad/Speechless face from the third illustration and his Smiling/Content face from his Prideful face in the first illustration to some extent.
  • Despite never receiving a name, in supporting material though, the Awdrys would call him Diesel 2 to distinguish him from Diesel 1 (from Duck and the Diesel Engine). Britt Allcroft also did this by calling him Class 40 on his nameboard, but told merchandise companies his name was "The Diesel".
  • Although Class 40 didn't appear in the fifth series, his theme from Bowled Out when he breaks down is heard in Cranky Bugs when Cranky is rescuing the engines from what remains of the shed. His theme can also be heard in other episodes from the fourth series.



* RWS only | ** T&F only