Derek is a diesel who is known for his initial "teething" troubles.


Thomas & Friends

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. Which is unfortunate since he really wants to work hard. But Derek is a likeable 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.

Technical Details


Derek is based on a BR Class 17, also known as the Clayton Diesel-electric Type 1. 117 members of this class were built between 1962 and 1965. Derek's problems were undoubtedly inspired by those of 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. Because of these problems, all Class 17s were withdrawn by the end of 1971, after less than 10 years of service. One Class 17, D8568, is preserved at the Chinnor and Princes Risborough Railway in South Oxfordshire.


Derek is painted in the British Railways Brunswick green livery with yellow warning panels. His window frames are lined white and he has the BR "Ferret and Dartboard" crest on his sides.


Thomas & Friends


Music Videos


Magazine Stories


Audio Files


First used Last used Sound Effect
Series 5 Series 5
Salty and Derek's Horn


  • According to Sharon Miller, she wrote Derek into an episode for Series 16 with a non-speaking role.[4] Bust My Buffers! was the episode in which this was to happen, but it never materialized due to "Paxman" in the script being mistaken for "Paxton" when it came time for the episode to be animated.[5]
  • Starting from Day of the Diesels, Derek's horn was reused for Salty. Before this, Derek's horn was also used for the foghorn in the sixth series episode, The Fogman and as Mavis' horn in the same series' episode, Buffer Bother.
  • Due to Derek's horn being a stock truck horn sound effect, it has been used in many other forms of media.
  • Derek was the first non-Awdry standard gauge engine to be introduced into the television series.
  • Derek was not named in any of his appearances as in his debut episode, Double Teething Troubles: he was only referred to as the new Diesel, or simply Diesel and in the music video Trying, the lyrics say "Who's that straining up the hill?" rather than Derek's usual name. He was only named in merchandise ranges.
  • His engine sound is shared with Rusty from the fourth and fifth series.
  • 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. The 1999 Official Website referred to Derek as Paxman Diesel.
  • The British Railways logo on his ERTL toy reads "Thomas Tank" instead of British Railways.
  • In his Wooden Railway prototype, Derek is seen with a greyish engine, unlike the black one presented in his final toy. His 2007 reissue sports the correct yellow engine.
  • His ERTL prototype shows him with a darker and different face and a darker colour scheme. His 2nd ERTL promotional artwork incorrectly depicts him with steam engine type wheels, a darker colour scheme, a grey undercarriage, square buffers and with no red buffer beam.


“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 series
“Hello! I'll soon sort this train out. You pull from the front and I'll push from the back. What fun.”
―Derek when he arrived to help Bill and Ben with their train, "Double Teething Troubles", fifth series
“Come on, push harder you silly diesel!”
―Ben pressuring Derek, "Double Teething Troubles", fifth series
“I'm overheating again.”
―Derek overheating, dragging the train to a stop,"Double Teething Troubles", fifth series



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