Sir Topham Hatt, nicknamed "the Fat Controller" is the manager of the North Western Railway.
Prior to his becoming Controller of the North Western Railway, Sir Bertram Topham Hatt owned a Sentinel steam lorry named Elizabeth, who notes that he wasn't the best driver. When he was a young man, Edward always took him aboard an old coach on his birthday. The Fat Controller later received his knighthood for his service to the railway industry. Sir Topham was also the controller of the Skarloey Railway, until Mr. Percival was hired to help him manage the ever-increasing size of his railway industry. In the sixteenth season, he gained a track inspection car named, Winston, which is often used as a private transportation vehicle on the railway.
Sir Topham Hatt married Lady Hatt, and is the grandfather of Stephen and Bridget Hatt. He has a twin brother, Sir Lowham Hatt, and his mother is Dowager Hatt. According to the Official Website, "we have yet to meet his children", presumably Charles Hatt, who became the second controller in the Railway Series.
As well as owning several engines, he owns a cat, two cars, and lives in a mansion somewhere on the outskirts of Wellsworth. However, when the engines misbehave, it's Edward that the Fat Controller turns to in order to calm everyone down and restore order.
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.
- Season 1 - Emily Helps Out, Percy Saves the Day, BoCo Helps Out (mentioned), Rocky Bridges, Edward Gets it Right, Henry's Happy Day, James and the Big Red Balloon, The Refreshment Lady's New Tea Shop, Harvey's Goods Train, Toby Saves the Lambs, Shortcut to Castle Loch, Rheneas' Roller Coaster, Salty's Story, Oliver and the Snowman, Fishy Troubles, Dashing Duncan, Big Strong Murdoch, Fergus and Diesel, Bulgy Returns, Harold and the Flying Climbers, The Grand Opening Arrives, Trust a Diesel (mentioned), Gordon and Spencer the Fast Engines, Thomas and the Snow, Rusty and the Bridge Repairs, and Thomas' Three Cheers
- Season 2 - Slow Coaches, Race with the Mail, Fergus and the Electric Engines, Duck and Dilly, Stanley to the Rescue, Henry's Fire Rescue (does not speak), Molly's Coal Delivery (mentioned), Small Engines, Mike and James, Gordon and the Bend, Hiro and the Coaches, Dave's New Home, Scottish Engines (mentioned), That's My Special, Disaster on Sodor, Stepney's Journey Out, and Flying Scotsman Departs
- Season 3 - Percy and the Other Railway, Old Slow Coach, The New Controller, Geoffrey and the Small Engines, Edward and the Thieves, Hector the Ballast Hopper, Saving Sidney, CoBo, Ghost Stories (mentioned), The Ghost of the Viaduct, Disappearing Diesels, Unique Stafford, Cold Crews, and Bertram and the Christmas Party (mentioned)
- Season 4 - Thomas and Algy, Best Decorated Engine (mentioned), Triple Trouble, Timothy and Dennis, Flora's Tram Coach, Brake Coaches, It's Not Easy Being Green, Special Engines, Neville at the Scrapyard, Geoffrey's Overhaul, The Wrong Sort of Coal, Broken Down Crane, James and Flynn, and George and Buster
- Season 5 - Sodor Snowstorm, The Big City Engine, Nigel (mentioned), Silver Steam, Sodor Wash Day, Stanley's Branch Line, Return of the Spotless Record, Samson and Logan, A Surprise for Oliver (mentioned), No Need for Timothy, Diesel and the Thunderstorm, Jerome and the Fish, and Old Enemies
- Season 6 - The New Diesel Fuel, Molly and the Fish, Overheated!, Toad and Hector (mentioned), Sidney's Search Party, Too Loud for Murdoch, Cold for Christmas (mentioned), Bulgy the Humbug, Diesel's Christmas Surprise (does not speak), James and the Royal Train, and Edward and the Express
- Season 7 - Young and Old, Toby and the Snowplough, Love for the Sea, and Salty and the Small Engines
- Season 8 - Sidney Saves the Day, Waddling Wilbert (mentioned), Henry Gets the Coaches, Lampless Lance, Bradford Returns, A Treasury Christmas (mentioned), Snowploughing at Christmas, The Diesel that Stole Christmas, Goodbye Glynn, and Glynn's Christmas Wish
- Thomas and the Storm
- Gordon and Spencer: An LNER Rivalry
- The Ghost Engine of Sodor
- The Curse of the Kipper
- Sodor and the Mystery of Christmas
- The Big Race
- The Adventure Begins (Sequel)
- The Return of Sailor John
- Due to political correctness, the Fat Controller is always known by his Sunday name of "Sir Topham Hatt" in the US.
- According to Elizabeth, the Fat Controller was a bad driver in his younger days. In the seventeenth season, it seems his skills have not improved.
- Throughout the television series, the Fat Controller is accompanied by two men in standard blue railway uniforms. They are presumed to be his bodyguards.
- The Fat Controller received his knighthood for his service to the railway industry.