- “"It's not fair!"
"What isn't fair?"
"Letting Branch Line diesels pull Main Line trains."
"Never mind, Gordon. I'm sure BoCo will let you pull his trucks sometimes. That would make it quite fair."
"I won't pull BoCo's dirty trucks! I won't run on Branch Lines!"
"Why not? It would be a nice change."
"The Fat Controller would never approve! Branch Lines are vulgar!"”
- ―Gordon and Edward arguing about BoCo and branch lines
Main Line Engines is the twenty-first book of The Railway Series.
Bill and Ben are a shameless pair. I meant to write about Main Line Engines, and give the twins a treat by letting them into the first story. But I couldn't keep them in order! Before I knew it, they had crept into the others. They even wanted me to change the book and make it about them!
But I have been very firm. I am still calling it Main Line Engines. That will serve Bill and Ben right for ragging poor Gordon so disgracefully.
He hasn't got over it yet!
Bill and Ben are tank engine twins that work at the China Clay Workings on Edward's Branch Line. One day they leave some trucks in a siding and leave for more, but return to find them all gone. Their drivers determine it was a "diseasel" that took them, and when Bill recalls a sign saying "coughs and sneezles spread diseasels", in his words, Ben blames him. Their drivers quiet them and formulate a plan. They find the "diseasel" on a siding, and manage to confuse him so as to make him giddy, but when Edward comes along he reprimands them and tells them to apologise to the diseasel, who calls himself BoCo. Edward sends them away, and he and BoCo joke about the twins.
Duck and BoCo are talking about Bill and Ben. Duck tells BoCo he has nicknamed them "The Bees", when James, who just arrived, claims he would simply blow smoke at bees to shoo them away. The next day, two porters are driving a trolley with a beehive on top when it falls off and bees swarm out. They decide to rest on James' boiler, but when one burns its feet, it stings James on the nose, and James runs away as he and his crew could not take it anymore. In the end, BoCo took the Express while Duck looked after his trucks, and that night the others talk about a red beehive on wheels.
Although the big engines are forbidden to go on the branch lines because of their weight, Gordon claims he is forbidden because they are "vulgar", and leaves to take his late train. He misses his "path" after a lady with a large floppy green hat confounds the fireman into thinking the guard had waved his flag, and in the end Edward's train leaves ahead of Gordon. However, this creates a huge disruption as the Wellsworth signalman is not informed, and Gordon is left on a siding at Brendam. The next day, Bill and Ben come into the yard, and tease him by "mistaking" him for scrap and arguing about how to dispose of Gordon. Gordon thinks they are serious, and when BoCo arrives, he asks for help. BoCo sends the twins away with his trucks, and Gordon has had great respect for BoCo ever since.
Edward reprimands Bill and Ben for what they did to Gordon, but told Gordon that he deserved it. He is later set to take some enthusiasts home, but finds it hard to move the train. After meeting up with Bill and Ben, Edward takes the enthusiasts away, but bad weather forces him to stop when a crankpin breaks, severely battering his splashers and frame up and out of shape. His crew take both side rods off, and Edward manages to struggle home. Edward is sent to Crovan's Gate to be mended, and BoCo does his work so well that he single-handedly changes Donald and Douglas' opinion about diesels.
- Bill and Ben
- Bill and Ben
- Sir Charles Topham Hatt II
- Thomas (does not speak)
- The Lady with the Floppy Green Hat (does not speak)
- Annie (cameo)
- Clarabel (not seen)
- Henry (mentioned)
- Donald and Douglas
- The Enthusiasts
- Bill and Ben (do not speak)
- Sir Charles Topham Hatt II (does not speak)
- Elsbridge Viaduct
- Tidmouth Sheds
- Brendam Docks
- The Scrapyards (mentioned)
- Suddery Junction (mentioned)
- Tidmouth Sheds
- Sodor China Clay Company
- Despite its name, a majority of this book takes place on Edward's Branch Line.
- This book marks the first appearances of Bill, Ben and BoCo.
- This book marks the last appearance of Edward in The Railway Series until James and the Diesel Engines.
- The events of this book take place in the latter half of 1965.
- This book marks the first time James is shown with his blue lining instead of his standard black lining.
- The word "diseasel" is a portmanteau of "disease" and "diesel".
- Buzz, Buzz is based on a real event in which six bees escaped from a hive at London Bridge Station.
- Wrong Road is based on a real event that occurred at Sittingbourne, Kent in 1911.
- Edward's Exploit is based on a real event of what happened to the crosshead assembly of an express train near Settle, North Yorkshire in 1960.
- Bill and Ben have no headlamps/headcodes throughout the book.
- In "Wrong Road" and "Edward's Exploit", Edward has "Express" Lamps instead of a "Branchline Passenger" one as he pulls his respective trains.
- In "The Diseasel":
- In the second illustration, Ben's face is discoloured.
- In the fourth and sixth illustrations, BoCo has the 'Express meat and fish' headcode, when he is supposed to have China clay trucks.
- In "Buzz, Buzz":
- In the fouth illustration, James' builder's plate reads "1943" despite the fact that he was built in 1912/13.
- In "Wrong Road":
- In the first illustration, Thomas' valence is curved and Annie is missing her face.
- In the sixth illustration, Bill and Ben are taller and thinner than they should be. Their faces are also shaped like ovals instead of circles.
- In "Edward's Exploit":
- In the first illustration, James' dome is red and his roof is black just like how it was in the Television Series whilst two workmen are transparently drawn.
- In the third illustration, the passengers and coaches are purple.
- In the last illustration, BoCo's number is missing.