Sir Topham Hatt, also nicknamed The Fat Controller, is the part-time manager of the North Western Railway on the Island of Sodor, and the main controller of the Transportonian Railway Co., with Dan Peterson as assistant controller. He's also a father figure to his engines.

Sir Topham Hatt is firm but funny and fair. He can be strict, but with a good reason and he deeply cares about the engines and also shows a fatherly side to them. He is quite a strong character and will remind the engines that he is in charge if they start to rebel against his authority. He does not stand bullying and even though he is usually serious, he does enjoy a good jolly laugh.

Despite his kindness and fairness, however, there are times where Sir Topham Hatt berates the engines for situations beyond their control. Like any son, he does hold a slight bit of respect for his mother, Dowager Hatt. But like all parental relationships, there are some things he finds more personal than others.

His voice source is Kerry Shale (US), Keith Wickham (UK/US), and Robin Smith Railway Adventures game ((US dub) and most US DVD menus).