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"Well, what I mean to say is..."
— Den thinking about what he's going to say before Dart interrupts him.
  • Class: Sentinel Diesel-Hydraulic
  • Designer: Rolls Royce Sentinel
  • Builder: Sentinel Waggon Works
  • Built: Sometime between 1959 and 1967
  • Configuration: 0-4-0
  • Top Speed: 20 mph

Den is a big diesel-hydraulic engine who runs the Sodor Dieselworks with his assistant, Dart.


In Day of the Diesels, Den and Dart took Thomas to the back shed of the Dieselworks while Percy, Diesel 10, and the other Diesels took over the Steamworks.

In the fifteenth season, he, along with Dart and Diesel, tried to find a Christmas tree for the Dieselworks whilst in competition with Thomas. Den later teased Flynn for spraying the Fat Controller and Gordon.

In the sixteenth season, he helped Thomas fix Ol' Wheezy and repaired Gordon's bufferbeam.

In the seventeenth season, Den, with Dart, help fixed a sputter in Salty's engine.

In the eighteenth season, Den, along with Dart, Sidney, and Diesel hid from Paxton, causing Paxton to search for them.

In the nineteenth season, he was sent to the quarry as a replacement for Mavis while she was at the Dieselworks. Initially, Den struggled with the troublesome trucks, but after some encouragement from Toby and Henrietta, he toughened up and finished his job. When Mavis came back, Den went back to the Dieselworks.

In The Great Race, Den, along with Dart and Paxton was part of Diesel's trick, which involved getting his three fellow diesels covered under a crate and mixing them in a heavy train, and when Diesel gave his whistling signal, the three would help him push, making it look as if Diesel was moving the train by himself, and as a result The Fat Controller would think Diesel is even stronger than Henry, thus taking him to the Great Railway Show instead of the big green engine. This should have been a workable plan, but the next morning Diesel refused to move his train from blocking all ways in and out of the yard, leading Thomas, who was in a hurry to practice his shunting in order to enter that very tournament in the very show, to move Diesel's Devious Train himself. When he whistled after a shunter coupled him up, the diesels mistook the tank engine's whistle as Diesel's horn and started pushing the train as they were instructed to. Thomas' shock in finding the train being mobile was equal to Diesel's when he saw the diesels were pushing the tank engine towards a collision with Norman at Knapford Junction, which indeed happened, making both tank and diesel engine's chance to enter the show go up in smoke. Later, Diesel confronted the three and nearly forced Dart off the Dieselworks turntable, but instead made Dart bump into a button, sending a crate down on Diesel. Diesel later escaped to Brendam Docks, and the three continued to hunt him down.


Den is the Diesel engine who runs the Vicarstown Dieselworks, repairing other Diesels. He is stately and deeply pensive. He tries to make sure everything he says is deeply considered, can often be heard muttering "what I mean to say is...", and can tend to over-think. He may come across as a little slow, but nothing could be further from the truth. He is rather astute and likes to take into account as much as he can with regards to a problem. Although he is not a worrier, he may tend to be on the fence about taking particular action over a matter before making a calculated, informed decision that will be worth the wait. Sometimes though, Dart, his assistant at the Dieselworks, can tell what he is thinking and cut to the chase a little quicker for the benefit of the other engines, which is why they support each other so well as a team. Den is a hard worker and is popular and well respected among the Diesels for fixing them with a whisk of his wheels, even if his tools may be old and shoddy and his machinery may be outdated. Although he is not devious, Den may have the occasional chuckle at an engine's expense.


Den is a Rolls Royce Sentinel Diesel-Hydraulic 0-4-0.


Den is painted slate grey and orange with cream lining. His buffer beams are painted with orange and black wasp stripes. He has the Sodor Dieselworks logo on each side of his cab.


Television series


Magazine stories

  • 2012 - Ol' Wheezy Wobbles and Thomas Toots the Crows (does not speak)
  • 2014 - Salty's New Friend (does not speak), Wobbly Ol' Wheezy, and Leaves on the Line! (does not speak)
  • 2015 - Bust My Buffers! (mentioned)

Voice Actors

  • Keith Wickham (UK/US; fifteenth season onwards, excluding Fiery Flynn)
  • Rupert Degas (UK/US; Fiery Flynn only)
  • Thierry Kazazian (France and French speaking Canada)
  • Ryuzou Ishino (Japan)
  • Sigbjørn Solheim (Norway; fifteenth - seventeenth season, excluding Day of the Diesels)
  • Fredrik Paasche (Norway; Day of the Diesels onwards, excluding the sixteenth and seventeenth season)
  • Burkhard Schmeer (Germany)
  • Piotr Bąk (Poland)
  • Víctor Covarrubias (Latin America)
  • Tiaggo Zambrano (Brazil)
  • Ángel Amorós (Spain)
  • Denis Bespalyy (Russia; nineteenth season onwards)


  • In the nineteenth season, Den gained a standard tail lamp, despite already having two the same design as his front lamps.


  • Wooden Railway
  • Take-n-Play (normal and talking)
  • TrackMaster
  • Mega Bloks (discontinued)
  • Wind-up (Japan only)
  • Pocket Fantasy (discontinued)
North Western Railway
ThomasEdwardHenryGordonJamesPercyTobyDuckDonald and DouglasOliverDaisy
Bill and BenHarveyEmilyArthurMurdochNevilleRosieWhiffStanleyHankFloraVictorCharlieBash and DashFerdinandScruffBellePorterTimothyMarionGlynnRyanSkiffDieselMavisDiesel 10'Arry and BertSaltyDenDartSidneyPaxtonNormanPhilipFlynnWinstonStafford