From Tony Grigg's notes on “The Island of Sodor”: Number 1 “Thomas” Thomas is a class E2 0-6-0T tank engine designed by Lawson B. Billinton, locomotive superintendent of the London Brighton and South Coast Railway between 1911 and 1922. The E2s were introduced in 1915 to replace earlier members of the E1 class, which had been scrapped. The last five in the ten strong class had extended side tanks to give a greater water capacity but all engines had two inside cylinders and driving wheels 4'6" in diameter. Thomas was bought to Sodor in 1915 to help with the construction of the North Western Railway, and remained after the completion. The engine was first used as Pilot at Tidmouth and then Vicarstown, before being drafted in to the Ffarquhar Branch line. The Real Lives of Thomas the Tank Engine - "Thomas"