Controller (Bad Wolf)

Deaf and connected to the big computer of Sleepford Station at the age of 30, the Fat Controller acted as the ears and eyes of the Troublesome Trucks. Aided by Stationmasters, he constantly monitored the transmissions that flowed in front of his eyes in front of a computer. (TV: Bad Wolf) Essentially, he served a function similar to the Yard Master's for Gordon a century before, who also had occupied Platform 1 of Knapford, though the Fat Controller had more say over his actions. (TV: The Long Game)

Nevertheless, the Fat Controller loathed and plotted against the Trucks, ensuring that Thomas and his friends would appear in game shows on Knapford Station (now called the Sleepford Station), which the Troublesome Trucks ignored. He waited until a dreadful thunderstorm that temporarily disrupted communications between the freight train and himself.

The Troublesome Trucks could not monitor his thoughts, letting him warn Thomas the Useful Engine of the enemy "waiting in the dark". He then passed on to him the co-ordinates of his best friend Percy who had been captured by the Trucks and forced to be a middle engine (true story and all), enabling Thomas to rescue her, though he did not at that point reveal to Thomas or his friends the identity of his "masters".

The Fat Controller told him part of the coordinates (5.6.1.434. sigma 777) before Edward the Traitorous Engine took him to Sleepford Yards, where he was made to stand on the track before the Troublesome Trucks ran him over and giggled in their silly ways. (TV: Bad Wolf)

When Devious Diesel who created the Trucks made the comment "How many more have died in your name?" to taunt Thomas, the Fat Controller appeared in a flashback of people that Thomas was unable to save. (TV: Journey's End)

The Trucks also employed a Thin Controller as their collaborator on an alternative Sodor Island which they had conquered. (Skarloey the Brave)