Sir Stephen Topham Hatt, better known as The Fat Controller, is the controller of the North Western Railway.
The current Fat Controller started out as "The Fat Director" and became the Fat Controller in succession of his father. During his time as director, he dealt with more minor issues, such as Henry getting stuck in the tunnel after refusing to get his paint spoiled in the rain. Taking rather harsh precautions, The Fat Director closed the long green engine in the tunnel where he was never to be released from it. However, when Gordon broke down with the Express near the tunnel, the Fat Director found it only fitting to release Henry and have him redeem himself and save Sodor's Premier Express.
Soon afterwards, the Fat Director became the Fat Controller when the North Western Railway was nationalized. This was also when he received his baronetcy as "Sir Topham Hatt" due to his contributions to the railway.
When the Fat Controller was on holiday, he was visiting the old Sodor Tramways Railway and met an old tram engine named Toby. His wife, Lady Hatt, and children, Stephen and Bridget, took a ride in his coach Henrietta and they all befriended the old steam tram. Unfortunately, soon after the Fat Controller left, there was trouble back on Sodor! Thomas had "broken the law" for riding on public rails without cow catchers and side plates on his branch line. The Fat Controller thought this was outrageous, but then he remembered the old steam tram from his visit to the closing tramway, and wrote a letter there to have Toby come and stay on the Thomas' Branch Line and occasionally at Ffarquhar Quarry with the new engine Mavis, all thanks to the kind-hearted controller.
The Fat Controller is called upon if there are issues such as troublesome engines, derailed trains and what not on the North Western Railway.
The Fat Controller purchased and frequently uses Winston, a private inspection car. Unfortunately, he has not exactly learned how to handle the car, much to Winston's dismay!