Sir Stephen Topham Hatt, more affectionately known as the Fat Controller, is the head 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 whatnot 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!
The Fat Controller's latest grand design is The Little Western Extension, a luxury tourist destination. However, the project has not had its problems, facing disasters such as tornadoes and assorted derailments. He eventually arranged a meeting for the other prominent business people on Sodor to invite others to the extension, but this meeting was disrupted by Carlo Debris' disgruntled workers.
When tied up in matters with the Ministry of Defense, The Fat Controller bestowed some extra responsibility upon his son Richard Hatt, allowing him to oversee Donald and Douglas' overhaul, and the subsequent meeting to discuss the Scottish Twins prolonged absence with the engines.
He arranged a meeting with Walter Richards of the Culdee Fell Railway about how the recent troubles on his railway (Culdee's derailment and Walter's apparent tendency to become scatter-brained) were making people higher up (The Barrane Family) think about having The Fat Controller succeed Walter, an act that would be impossible due to The Fat Controller's imminent retirement and Richard not being able to handle the stress of suddenly handling two railways. He assured Walter about how he and the other railwaymen wanted the best of him before leaving on Winston.
The Fat Controller checks in on his son Richard following his failure with the suggestion box. He reminds this son that similar events transpired following his announcement of the Little Western Extension Project. When he discovers an unopened suggestion which suggests constructing a branch line from Arlesburgh Harbour to Harwick, he takes the idea as his own, quite impressed by it.
As a means of keeping the railway competitive and rejuvenated, Sir Stephen arranges for several preserved engines to visit and perform rail-tours on the railway. Despite Richard's misgivings about the strategy, Stephen places him in charge of the photo-ops on the Ffarqhaur Branch Line for one of the visitors, Asbestos. This scheme goes away however when a passenger overhears Richard Hatt discussing Percy's overexposure to Asbestos the engine, which they mistakenly interpret as an exposure to the toxic carcinogen on the railway. Subsequently, an angry mob confronts the Fat Controller, putting him and the railway on trial for the supposed outbreak. Rather than hire a real attorney, Sir Stephen solicits Walter Sliggs to represent him, believing that Sliggs' experience in the courtroom would suffice as a representative. However, Sliggs' antics in the courtroom fail to prove the Fat Controller's innocence, prompting the judge to consider finding him guilty. However, a surprise witness in the form of an out of control Asbestos crashing into the courthouse brings the entire misunderstanding to a close. Upon learning Richard's poorly chosen wording was responsible, Sir Stephen scolds his son for potentially getting him wrongfully imprisoned.
The Fat Controller is a good, strong leader who can take charge of any situation when he's needed. He is proud of his railway and his engines, and is proud to be working on what he considers to be the most amazing railway in the world.
- Season 0: Old Groaner
- Season 1: Lift Bridge, Swagger and Swerves, Splatter (mentioned), Dodge (remastered version only), Life Boats (mentioned), Bulldozer, Feeling Lucky?, Improvisation (mentioned), Rising to the Occasion, Snow Blind (remastered version only), Buffer Bashing, Scruff's Scaffolding (mentioned), Rendezvous with Disaster, Conspiracy Theory (mentioned)
- Season 2: Paxton and Norman, Grim Messengers of Doom, Scot-free, Mavis and the Tornado, Rosie, Rock-Star (does not speak), Waterworks, Pummeling Percy (mentioned), Munitions (mentioned), Blunderbuss, Swan Dive, Aura of Menace, Henry and Kurt, All the World's a Stage (cameo), Swashbuckler, Thomas and the Fortune Teller (does not speak), Self-Fulfilling Prophecy
- Season 3: Marion Saves the Day (mentioned), This Too Shall Pass (mentioned), Perhaps He's Got a Corset (mentioned), Samson, BoCo, and the Man in the Hills (cameo), Culdee Fell, The Suggestion Box, Ice Breaker (does not speak), Percy and Asbestos, James Goes On A Streak (does not speak), Stafford's Request (mentioned)
- Web Clips: The Fat Controller, the Stationmaster, and the Raiboat - Meet the Characters!, Thomas the Tank Engine 70th Anniversary Celebration! (cameo), Timothy, Bill, Ben, and Marion - Meet the Characters! (cameo), Emily, Toby and Henrietta - Meet the Characters! (mentioned)
- With a current grand total of 25 episodes, the Fat Controller has had the most speaking roles in the series by far, with the second most being 16 (tied between Derek, Duck, Edward, James, Percy and Sir Handel).