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"Hey you two. This new Diesel's got a toothache. Good luck!"
Percy, Double Teething Troubles, fifth season

  • Class: BR Class 17
  • Designer: Clayton Equipment Company and Beyer, Peacock & Co.
  • Builder: Clayton Equipment Company and Beyer, Peacock & Co.
  • Configuration: Bo-Bo
  • Top Speed: 60 mph
  • Built: sometime between 1962 and 1965

Derek is a Diesel, best known for his initial "teething" troubles.


The Fat Controller realised Bill and Ben needed help and sent for Derek, but Derek's cooling system overheated on Gordon's Hill and BoCo had to come to the rescue. The news of the rescue went through the North Western Railway's rumour mill in due course, until a confused Percy informed Bill and Ben that Derek had a toothache. Bill and Ben were apprehensive of Derek as a result, but forgot their fear when Derek's cooling system overheated yet again and they had to help him home. Derek was then sent to the Works to be mended.

Derek returned later in Calling All Engines!, pulling a goods train up Gordon's Hill.

According to the official website, Derek now spends most of his time at the quarries and clay mines near Brendam Docks working with Bill and Ben.


Derek is a jolly, enthusiastic Diesel engine, who was brought in to assist Bill, Ben, and BoCo at the China Clay quarry. Unfortunately, due to his engine, he is highly prone to teething troubles, namely overheating and suffering frequent breakdowns, for which he is apologetic for the inconvenience. As a result, he spends many a day having his engine tended to. But Derek is a likable chap and even Bill and Ben decided that they liked him due to his friendly nature. Derek has an infectious charisma, is keen to help anyone around him, and has a passion for sorting things out in a jiffy - if his cooling system lets him.


Derek is based on a BR Class 17, a Clayton and Beyer-Peacock Diesel-electric Type 1.


Derek is painted in the British Railway's green livery with yellow warning panels.


Television series

He also made a cameo in a fifth season music video.


Voice Actors


  • Starting from season 14, Derek's horn was reused for Salty.
  • Derek was the first non-Awdry standard gauge diesel engine to be introduced into the television series.
  • Derek was not named in his appearance in "Double Teething Troubles": he was only referred to as "the new Diesel". It was not until the release of the merchandise that Derek's name was revealed.
  • Originally, Derek was going to be named "Paxman", but it was changed for fear it would offend the Paxman brand of Diesels, or refer to celebrity Jeremy Paxman.
  • In addition, the 1999 official website referred to Derek as "Paxman Diesel".
  • The British railways logo on his ERTL model reads "Thomas Tank" instead of British Railways.
  • Derek's problems were undoubtedly inspired by his basis, as the twin Paxman engines of the real Class 17s were unreliable, being prone to problems with the camshaft, cylinder head, and other areas.


"You do look glum!" sighed Duck.
"It's the new diesel's fault," replied Bill. "He's got toothache!"
"Toothache? He's got teething troubles. That means he's new and is causing some problems. In his case it's in his cooling system."

- Duck, Bill and Ben talk about Derek, "Double Teething Troubles", fifth season.



Merchandise Gallery

North Western Railway
ThomasEdwardHenryGordonJamesPercyTobyDuckDonald and DouglasOliverBarryThe Austerity EngineThe Red EnginesDaisyBoCoBearThe Works DieselPip and EmmaPeel Godred Engines
HarveyEmilyFergusArthurMurdochMollyNevilleRosieWhiffBillyStanleyHankFloraVictorCharlieBash and DashFerdinandScruffBellePorterDerekDiesel 10'Arry and BertSaltyDennisDenDartSidneyPaxtonNormanFlynnWinstonStafford

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