Thomas the Tank Engine Wikia

“Invisibility On!”

Merlin is an experimental tender engine with three funnels who believes he has the power to turn invisible.


Thomas & Friends

When Thomas travelled to the Mainland, he befriended the experimental engines: Merlin, Theo and Lexi. Merlin sails through life, full of confidence, believing that he has the ability to become invisible. Helping to hide Thomas from Frankie and Hurricane, he promised to help him find his way back to Sodor. Later, Merlin - along with the other experimental engines - helped Thomas rescue James, who had been trapped in the Steelworks. [1]

Afterwards, Merlin offered to stay at the Steelworks to help Frankie and Hurricane and helped Thomas to convince the other experimental engines, Theo and Lexi, to do the same. [1]

When Merlin first came to Sodor, he showed everyone he can become invisible, except Percy, who was upset he did not get to see him. When Percy heard an unfamiliar whistle in the distance but could not see who it belonged to, he assumed it was Merlin, and rushed off to tell Thomas. However, the "invisible engine" turned out to be Trevor. [2]


Merlin sees himself as a hero. He is proud and confident of his abilities and in particular his special skill - the ability to make himself invisible. All he has to do is say "Invisibility on!" and shut his eyes and he is convinced that nobody can see him. He knows he was specially designed in order to be hard to see and his three funnels - which were intended to disperse his smoke and steam - are there to prove it. What Merlin does not know is that his experiment does not work. Merlin wants to be able to prove himself and show everyone all the things he can do. He honestly believes anyone can do anything they set their mind to or at the very least, they can try! Merlin is fun and funny and wants to be a good friend, but his lack of judgement and sense of his own limitations can create its own challenges.

Technical Details


Merlin is based on a London and South Western Railway (LSWR) N15 Class, referred to as the "King Arthur" class by the Southern Railway, specifically No. 783 Sir Gillemere. In 1940, Sir Gillemere was fitted with three stovepipe chimneys by Oliver Bulleid as a wartime experiment. The way the smoke was spread out was meant to make the trains less visible to bombers overhead. The experiment was not a success, and the engine was quickly converted back to normal. No. 783 became No. 30783 under British Railways after nationalisation in 1948 and was withdrawn in March 1961.

Merlin's name is likely taken from another King Arthur engine, No. 740 Merlin. A single King Arthur is preserved as part of the National Collection, No. 777 Sir Lamiel, and is based at the Great Central Railway, currently awaiting overhaul.


Merlin is painted silver with a red running board and wheels, and black smoke deflectors. He has red and gold nameplates on his sides. His number (783) is also painted white on his front buffer beam, the sides of his cab and tender.


Audio Files


First used Last used Sound Effect
Journey Beyond Sodor Series 22


  • Merlin's whistle sound is Spencer's basis, an LNER A4 Pacific 3-chime.
  • Merlin's tender is a modified version of Bert's.
  • Merlin is the second character to have his basis named in the television series, with BoCo being the first.
  • Merlin along with Beresford are the only characters introduced in Journey Beyond Sodor to appear in an episode.
  • Merlin's TrackMaster toy depicts him very metallic, unlike how he appears in the show.
  • Merlin's eccentric rods are not animated properly as they do not complete a full rotation around his larger connecting rods.
  • Merlin, Hurricane and Frankie are the first engines in the television series to have their numbers written on their front buffer beams. Prior to this, the feature was exclusive to The Railway Series.
  • According to Michael White, Merlin may have been intended to appear in the twenty-fourth series double length episode, Thomas and the Royal Engine, but was dropped for unknown reasons.


“I'm invisible! Or can't you see? Who said that? You ask. It's only me! You look surprised, but have no fear! It's just a little trick to make myself disappear!”
―Merlin's solo in 'We Can't Do Anything'
“We can't do anything!"
"But we can try! We can give anything a try! We will give anything a try! Isn't that right?”
―Merlin responding positively to Lexi and Theo, Journey Beyond Sodor
“This is my first time on the Island of Sonar, my friend Thomas works here."
"Do you mean Sodor?”
―Merlin and Cranky, Seeing is Believing


External Link


* RWS only | ** T&F only