Thomas the Tank Engine Wikia
Thomas the Tank Engine Wikia
This article is about the engine. You may be looking for the Story Library book.

“For a diesel, yon BoCo's nae sich a bad sort of engine.”
Donald and Douglas's remark about BoCo[src]

BoCo is a green mixed-traffic diesel engine, who primarily works on Edward's Branch Line and occasionally on the Main Line.


The Railway Series

BoCo was built for British Railways on 29 September, 1958, and along with the rest of his class worked in the Barrow-in-Furness area from 1962. In 1965 he found his way to the Brendam Branch Line. Sir Topham Hatt expressed interest in buying him, and British Railways allowed him to keep the engine for trials. These proved satisfactory, and BoCo was purchased.

BoCo once accidentally took Bill and Ben's China clay trucks. The twins decided to play a trick on him, playing on their identical looks to make the diesel think that one engine was vanishing and reappearing around him. Edward was nearby to sort out the confusion and Bill and Ben soon came to respect BoCo.

Duck, who was suspicious of diesels due to his own experience, nevertheless took quickly to BoCo when the diesel took trucks to Tidmouth and found out that he was good friends with Edward. The two started talking in the shed, but were interrupted when James arrived and called BoCo a "buzz box." Ironically, James was attacked by a swarm of bees the next day and so BoCo had to take the Express. Although things had smoothed over between James and BoCo, Gordon was furious that a mere branch line diesel got to pull a mainline train. Gordon was later stranded on Edward's branch line due to a signalmen's error. Bill and Ben were quick to tease Gordon and jokingly threatened to haul him away as scrap or dump him into the harbour. When BoCo arrived with some trucks, he sent Bill and Ben to work and the relieved Gordon felt he owed his life to BoCo.

When Edward had trouble pulling an enthusiasts' train, BoCo helped Duck to shut the big engines up, who said Edward should be preserved. BoCo later filled in on the branch line while Edward was at Crovan's Gate Works. Donald and Douglas were the last engines to accept BoCo.

BoCo showed Diesel 40125 around but abandoned him when the new diesel insulted the Fat Controller for keeping steam engines in service.

BoCo tried to cheer Gordon up when he got into trouble for spraying ashes onto a wedding party and later helped him to Barrow-in-Furness when his fire bars collapsed. BoCo also helped Edward to the Works when his bogie wheel snapped off and ran the branch line while Edward was undergoing an overhaul. BoCo met Victoria when Edward stopped at Wellsworth with her while being brought back to service on Thomas' Branch Line and later laughed at Donald after his accident with a set of buffers.

Thomas & Friends

Bill and Ben were once called to the yard to help shunt trains for BoCo. The two began fighting after an incident with the turntable and soon began to give each other the silent treatment. Edward thought this attitude was counterproductive, so BoCo came up with a plan: convincing the Fat Controller to let him take a special, BoCo's own heavy goods train was left behind, with only Bill and Ben to pull - neither would be strong enough to pull the train alone, so the two had to compromise and work together to finish the job. [5]

When the first eight engines went to the Mainland, BoCo was part of a group of engines designated to take over the major jobs of the railway. [6]

Eventually, BoCo lost his buffer in keeping the twins in line and the Fat Controller decided to bring in a new diesel, Derek. Derek, however, had major "teething" troubles and was prone to overheating. BoCo had to bring workmen to help Derek when he first broke down. [7]


BoCo is a tame diesel engine, who is sensible, kind, and has a decent sense of humour. He is also very disciplined, as seen as he stops Bill and Ben from their pranks. Upon his arrival, he was unfortunate enough to be set upon by the mischievous Bill and Ben, when, thinking he had intentionally stolen their trucks, they pretended to be one engine and nearly made his eyes pop out. BoCo is now wise to the tank engine twins' pranks though he still somewhat humours them to a point. He is also good friends with Bill, Ben, Edward, and Duck. He is a true friend and is often willing to stick up for the underdog. BoCo is firm, but fair and friendly in his nature, not being afraid to speak his mind. Even Gordon soon thought of him in high regard when he "saved" him from Bill and Ben's antics. BoCo upholds a more praiseworthy and respectable, likeable image for diesel engines everywhere, being happy to show the more pompous steam engines that diesels have their uses. BoCo helps bring good order across Edward's Branch Line, even occasionally pulling Main Line trains, as the Fat Controller recognises how versatile he is.

Technical Details


BoCo is based on a British Rail (BR) Class 28 Co-Bo diesel-electric engine. D5701 is also based on this engine. BoCo's name is derived from his Co-Bo wheel arrangement, though reversed as the Rev. W. Awdry thought "BoCo" sounded more affectionate. These engines were initially used on the "Condor" express freight services but the class's Crossley engines quickly proved problematic. They suffered frequent failures, and in 1961 the entire class was handed back to the manufacturer for remedial work on the engines, and to cure problems with cab windows falling out while running. Upon return to service in 1962, all members of the class were allocated to Barrow-in-Furness. BoCo was susceptible to the mechanical failures of his class - according to the Awdrys, however, the Fat Controller eventually found a fix to prevent these malfunctions. The real engines were not so fortunate, and most were withdrawn and scrapped by 1969.

BoCo's number belonged to a real BR Class 28. The real D5702 was built in 29 September, 1958, and was withdrawn on 7th September, 1968, before being scrapped at J. Cashmore Scrapyards the following year.

In the annuals, BoCo mentions a brother of his - D5705, a real preserved engine, who is the last surviving Class 28. In another annual, BoCo claimed to have a twin called "CoBo" in order to play a trick on Bill and Ben.


BoCo is painted in the BR Brunswick green livery. He has yellow warning panels on his front and back end. In the television series, BoCo is painted in a more vibrant shade of green without yellow warning panels on his front and back end. "D5702" is painted on the sides of his cab in white.

In The Railway Series, BoCo has a yellow face. However, in Main Line Engines, he was first depicted with a yellow end from below his mouth to half-way up his nose. The top half of BoCo's nose and his eyes were in his green paintwork. This is evident in the fourth and sixth illustrations of "The Diseasel" as well as the last illustration of "Edward's Exploit". This type of face was also shown in "Old Stuck-Up" in "James and the Diesel Engines". Since he had two faces at each end of him, this could explain why his face differs in different illustrations. In the television series, he has a grey face on one end only to match the other characters.



Magazine Stories

BoCo also appeared in the magazine stories, Bill and BoCo, Blowing About!, Company for Cranky, Diesel Display, Diesels with Measles!, It Takes Two!, Making a Mess!, Sea-Bound Salty, Smoky Sky, So Much Smoke!, Spotting Shapes, Track Trouble! (mentioned) and White Van Man (cameo).

Annual Stories

Video Games

Audio Files



In the second to fifth series, BoCo reused Diesel's horn in a lower pitch.

First used Last used Sound Effect
Series 2 Series 5

In the third series, BoCo reused Mavis' original horn in a lower pitch.

First used Last used Sound Effect
Series 3 Series 3


  • BoCo's name is often mis-capitalised as "Boco". One example of this is on his nameboard.
  • On the cover of the My Thomas Story Library, BoCo's wheel arrangement shows a Co-Co wheel arrangement. This was fixed in the 2011 re-release.
  • In the television series, BoCo and Daisy shared some of the same faces, with Daisy's face having added make-up. They also share the same chassis and powered "Bo" bogie.
  • BoCo is the first of two characters to mention their own real-life basis in the television series, the other being Merlin.
  • Four of BoCo's face masks are now owned by Twitter user TomsProps.
  • BoCo has had two different horn sounds over the years:
    • In the second series, he shared the same sound as Diesel's, but in a lower pitch.
    • In the third series, he received a two-toned horn, similar to Mavis', but some steps lower-pitched.
    • In the fourth series, he regained his original horn sound after it was reused for Daisy.
  • In a 2015 interview with Sodor Island Fansite (SiF), railway consultant Sam Wilkinson expressed interest in reintroducing BoCo into the CGI Series, if this had happened, this would have become his first appearance and speaking role since the fifth series episode Double Teething Troubles.
  • BoCo's name is a joke on his wheel arrangement, Co-Bo.
  • On August 28, 2021, it was revealed that BoCo's model is in the possession of Sam Wilkinson.


“...Even you don't come in our yard without asking. And you only take the trucks we give you. But," they both squeaked indignantly, "This 'diseasel' didn't even ask. He just took the lot!"
"There is no cause to be rude"
said Edward severely. "This engine is a Metropolitan-Vickers, diesel-electric, Type 2."
The twins were abashed. "We're sorry Mr-er..."
"Never mind,"
he smiled, "call me BoCo. I'm sorry I didn't understand about the trucks.”
―Edward introduces BoCo to Bill and Ben after some confusion, "The Diseasel", Main Line Engines
“For a diesel, yon BoCo's nae sich a bad sort of engine."
"That from the Caledonian twins is high praise indeed.
―Donald and Douglas, the last to accept diesels, praise BoCo, "Edward's Exploit", Main Line Engines



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