The Fat Controller is a title for Sir Topham Hatt who is the manager of the North Western Railway. This title came to light in the third book of the Railway Series called James the Red Engine which was shown in the foreword of this book upon nationalisation of British Railways in 1948.
The Fat Controller was the successor to The Fat Driector. This former title was used in The Three Railway Engines when Henry refused to come out of the tunnel. He helped the passengers to pull and push using a rope which his doctor forbids him in pushing from behind and pulling from the front. He later gave up, had another engine to take Henry's passengers and also, bricked Henry up inside the tunnel. Later, the Fat Driector didn't like big engines since Gordon bursted his safety valve and always broke down. The stout gentleman told Henry to pull the train with Edward and he loses his top-hat to a ram when the train went faster and faster from Henry's tunnel.
In Thomas the Tank Engine, he tries to calm Gordon down but the big blue engine wanted to pay Thomas out for all of his teasing. The Fat Driector tried to call for Thomas to stop when the coupling wasn't fitted between Thomas's back end and the front of the first express coach. He tells Thomas to be more careful with the Troublesome Trucks after they push Thomas down Gordon's Hill and finally after shunting trucks, Thomas was glad to do it. The Fat Driector's final moment was when he awarded Thomas his Branch line after saving James in a nasty accident by using The Breakdown Train.