Sir Topham Hatt, nicknamed "the Fat Controller" (previously known as "the Fat Director"), is the manager of the North Western Railway.
Sir Topham Hatt is firm but fair. He can be strict, but also shows a fatherly side to the engines. He is quite a strong character and will remind the engines that he is in charge when they start to rebel against his authority. He does not stand bullying and even though he is usually serious, he does enjoy a good laugh. Despite his kindness and fairness, however, there are times where he berates the engines for situations beyond their control.
Sir Topham Hatt is a short, stout gentleman. He is usually dressed in a black suit with grey trousers, a cream or yellow waistcoat, a black tie and a top hat. He is most often depicted as having thinning grey hair and blue eyes.
- Season 100 - Geoffrey's Real, Toby and Philip (mentioned), Henry the Warrior, Trouble with Brakevans, Samson's Waste Dump, Jealous James, Skiff and the Lighthouse, The Railcar and the Passengers, Scottish Engines, Salty's Secret Story, Oliver and the Coaches, Spencer the Show-Off, Mike and James, Snowploughing at Christmas, The Christmas Engines, Duncan's Dilemma (mentioned), Ryan and the Snow, Henry in the Darkness, Timothy and the Aquarium, Sidney Helps Out, Skiff and the Dolphin, and Thomas the Hero
- Keith Wickham (UK; Hero of the Rails onwards - US; The Adventure Begins onwards)
- Kerry Shale (US; Hero of the Rails - eighteenth season)
- Blas García (Latin America; Hero of the Rails onwards)
- Kōhei Miyauchi (Japan; first - fourth seasons)
- Takeshi Aono (Japan; fifth - eighth seasons)
- Rokurō Naya (Japan; Calling All Engines! - eighteenth season, excluding Tale of the Brave)
- Kan Tanaka (Japan; Tale of the Brave onwards, excluding the eighteenth season)
- Øyvind Borgemoen Lyse (Norway; Hero of the Rails - Tale of the Brave)
- Fredrik Steen (Norway; eighteenth season onwards)
- Michel Lasorne (France and French speaking Canada; eighth - twelfth seasons)
- Bernard Demory (France and French speaking Canada; Hero of the Rails onwards)
- Enzo Avolio (Italy)
- Michael Bideller (Germany; twelfth season only)
- Eberhard Haar (Germany; Hero of the Rails onwards)
- Thomas Fritsch (Germany; Audio Books: 1 - 5 only)
- Jörg Gillner - (Germany; Audio Books: 6 - 16 only)
- Aku Laitinen (Finland; Hero of the Rails onwards)
- Mikołaj Klimek (Poland)
- Nir Ron (Israel)
- Maarten Wansink (The Netherlands)
- Troells Toya (Denmark)
- Luiz Carlos de Morais (Brazil; twelfth season onwards)
- Roberto Cuadrado (Spain; Hero of the Rails onwards)
- Rin Tripa (Romania)
- Alexander Kotov (Russia)
- Due to political correctness, the Fat Controller is always narrated as "Sir Topham Hatt" in America.
- The Fat Controller's television model from Lady Hatt's Birthday Party appeared in the 2009 "Children in Need" charity single and was animated using stop-motion.
- In an earlier draft of Thomas and the Magic Railroad, Diesel 10 called him "Fat Hatt", a combination of his nickname and his real name.
- According to Elizabeth, Sir Topham Hatt was a bad driver in his younger days. Since he started driving Winston, it seems his skills have not improved.
- The Fat Controller's office set was part of an exhibit at the Hangaram Museum in Korea in 2010.
- Large scale and miniature models of Sir Topham Hatt are currently in the safe hands of the Top Props preservation group, after they were sold by The Prop Gallery. A large scale walking model of Sir Topham Hatt was also sold by The Prop Gallery.
- Throughout the television series, Sir Topham Hatt is accompanied by two men in standard blue railway uniforms. They are presumed to be his assistants. In Percy and the Calliope, the narrator refers to them as "helpers".
- The Fat Controller received his knighthood for his services to the railway industry and an award for "Services to Transport".
- In the book, Thomas-saurus Rex, it states that Sir Topham Hatt used to be called "Little Topham Hatt" in his youth. His grandfather also appears in the book.
- Sir Topham Hatt's television series model had eyebrows inconsistently. Between the sixth and eleventh seasons, the model mainly did not have them at all.
- The alternative rock band Catherine Wheel released a song named after The Fat Controller called "Here Comes The Fat Controller" on their 1997 album Adam and Eve.
- From the thirteen season to the fifteen season, Sir Topham Hatt was referred to as "Bertram".
- In most episodes and specials, Sir Topham Hatt is seen writing with his right hand. But in No Help At All, he is seen writing left-handed, this could most likely be a mistake.
- A photo of Sir Topham Hatt from the first season episode Trouble in the Shed was shown on a web-exclusive video of Last Week Tonight with John Oliver.