Thomas the Tank Engine Wikia
Thomas the Tank Engine Wikia

Rex is a small green tender engine who lives and works on the Arlesdale Railway. He enjoys nothing more than teasing Mike. He is a hard worker, but sometimes has problems with traction.


The Railway Series

Rex is based on a design by Henry Greenly, and was built by Davey, Paxman of Colchester in 1923 at the same time as River Esk was for the Ravenglass and Eskdale. He was found to be powerful but erratic and was sent to the Yorkshire Engine Co. for rebuilding in 1928 at the same time as River Esk, and for the same reasons. Walschaerts valve gear, substituted for the poppet gear originally fitted, gave beneficial results.

After Rex's old line in England closed down in 1967, he, Mike, and Bert were bought by Sir Topham Hatt and transferred to the Arlesdale Railway for mining and tourist traffic. Since coming to Arlesburgh Rex has been found reliable and free steaming, but needs careful handling with any but the lightest loads, having an unfortunate tendency to slip. After the railway secured a deal to transport wool to Arlesburgh, Rex was chosen to pull the first train. But after Willie, a negligent farmhand spilled some wool bales on the rails, Rex hit them and derailed. His train was rescued, but Rex had to remain there for several days until he could be lifted out.

Rex, along with the other small engines were offered to be in the Reverend's next book if they behaved, when a rescue team went on a mission to look for Duke.

Rex later broke down when his steampipe was leaking, but when his driver used his radio telephone to contact for help, Frank was available, and took his train while Rex backed into a loop and went back home for his driver to mend his steampipe.

Thomas & Friends

When Marion was heading to the construction yard for the Harwick Branch Line, she was startled by Rex, Bert and Mike at Arlesburgh West. Rex told her that their railway catered to passengers, as well as ballast and wool. Marion had never seen such small engines, and thought that they must be magic. Later, Thomas arrived at the Junction, dismayed that the Fat Controller had sent him to work on the new branch line, while Ryan looked after his own. He, Mike and Bert sang Never Overlook a Little Engine to lift his spirits. Later on, when Marion arrived at the Junction again and addressed the three engines as "magic engines," Rex joked that she was talking about Mike, and he and Bert left before Marion could notice them, leaving Mike. Two nights later, Thomas was chasing Sailor John, Skiff and the Pirate Ship. When they reached the junction, the small engines were woken up by Ryan, who believed he saw pirates, and quickly thinking, they shunted a train of hoppers off the chute and onto the standard gauge line to slow them down. The ship crushed most of the hoppers immediately, but one was caught under it, causing it to lose speed. Ryan then managed to derail the ship.

Rex reprised his roles from the Railway Series, from when he and Bert teased Mike about his whistle to when he derailed from crashing into the wool bales that fell on the tracks thanks to Willie.

In the twenty-first series, instead of bringing presents to the children this year, Rex brought a truck of fake snow for the fan at the end of his train to blow on it, making it look like it was snowing. Daisy, who was present when it happened, was not happy about it since it was not the way she wanted it.

Percy later told him, Bert and Mike about a railway show for little engines that was being held at Ulfstead Castle, which made him not collect wool from a farmer. Rex was later carried on a flatbed by Ryan to the castle for the show.


Rex is a playful green miniature engine with a strong sense of humour. He is a hard worker, and is the natural leader of the little railway engines (in spite of the fact that Mike prefers to think he’s the leader). Rex is very proud of his railway and a great friend to the other engines, but he can’t help teasing Mike to stop him getting too full of himself. Most of the time Mike manages to return the banter, but sometimes he gets a little wound up. Luckily Rex is very good at helping Mike see the funny side again, and is generally kindhearted and friendly.

Technical Details


Rex is based on the Ravenglass and Eskdale Railway's River Esk.


Rex is painted green with red and yellow lining. He has a brass dome, brass builder's plates on the sides of his cab, red nameplates with gold writing mounted on each side of his boiler and "ARLESDALE" written on the sides of his tender in yellow. In the Railway Series his wheels are painted black, but in the television series they are green.


Audio Files


Since Sodor's Legend of the Lost Treasure, Rex reuses Mac's original whistle. Which is also Sir Handel‘s Season 10 onwards but at a high pitch.

First used Last used Sound Effect
Sodor's Legend of the Lost Treasure Active


  • Rex reuses Mac's original whistle sound, which is also a seven-step higher pitched version of Sir Handel's current whistle sound.
  • In Rex's trading card promo, he is incorrectly depicted as a 4-8-2 along with Mike and Bert.
  • In the CGI series, Rex's eccentric rods are inconsistently animated properly as they do not complete a full rotation around his larger connecting rods.
  • Rex is the first engine in the Television Series since City of Truro to not be available in Wooden Railway.


“What do you think of our 'chute?" said a voice. "Good, isn't it?"
Duck blinked. Standing beside him was a small green engine.
"Where did you spring from?"
asked Duck.
"I've been here all the time,"
smiled the small engine. "I'm Rex, and you, I'm sure, are Duck."
"How did you know?"
"That's easy; there's only one Great Western engine in these parts.”
―Duck meeting Rex, Small Railway Engines