Thomas the Tank Engine Wikia
Thomas the Tank Engine Wikia

Derek is a British Rail Class 17 diesel who is known for his initial "teething" troubles.


Thomas & Friends

The Fat Controller realised Bill and Ben needed help with their work 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 and was seen pulling a goods train up Gordon's Hill. [4]

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. However, 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 British Rail (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 Because of these problems, all Class 17s were withdrawn by the end of 1971, after less than 10 years of service.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, England.


Derek is painted in the BR Brunswick green livery. He has yellow warning panels on his front and back ends. He has white lining on his window frames 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


  • According to Sharon Miller, she wrote Derek into a sixteenth series episode with a non-speaking role.[5] 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"
  • Starting from Day of the Diesels, Derek's horn sound was reused for Salty. Before this, Derek's horn sound was also reused for the foghorn in the sixth series episode, The Fogman and Mavis in the same series' episode, Buffer Bother. It was mistakenly used for Diesel 10 in some merchandise and some games. It was also mistakenly used for Diesel in Fun Cubes.
  • Due to Derek's horn being a stock truck horn sound effect, it has been used in many other forms of media, such as the Tom and Jerry Show episodes, "Molecular Breakup" and "Road Trippin'" And the Cars Toon Mater's Tall Tales Episode Unidentified Flying Mater.
  • 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. This makes him the first character to only be named in merchandise ranges.
  • Derek's engine sound is shared with Rusty, Mavis, BoCo and 'Arry and Bert.
  • Diesel would later reuse the same sound in one scene of Calling All Engines!.
  • 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 BR crest on Derek's 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.
  • Derek's ERTL prototype shows him with a darker and different face and a darker colour scheme. His second 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.
  • According to his 2001 Wooden Railway Character Card, Derek was formerly known as Paxman.


“You do look glum", sighed Duck.
"It's the new diesel's fault",
replied Bill. "He's got (a) toothache!"
UK: "Toothache? He's got teething troubles." US: "He hasn't got a toothache. He's got teething troubles. That means he's new and is causing/this causes 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



* RWS only | ** T&F only | --- Dropped

* RWS only | ** T&F only