One day, Jacob and Henry had to take a train of scrap from Sodor to The Other Railway. When they got there, they found William. William explained to them that he had been there since 1975 and was scheduled to be broken up the following week. Jacob, feeling bad for William, decided to buy him and take him to Sodor. After speaking with the yardmaster, Jacob did just that, and he and Henry took William to the Sodor Steamworks to be repaired.
Once William was fully repaired, he started living at Knapford Sheds. He then told the Knapford Sheds Engines about his past. He told them how he and his original owner were best friends, until his owner left him in a garden for years. Then, after his owner died in 1975, his son sold William to a scrapyard on the Other Railway, where he stayed until Jacob found him 48 years later.
William is a kind old engine. He has a great hatred of diesels after being replaced and nearly scrapped by them.
William is based on a Philadelphia and Reading Railway C1a Class 4-4-4 locomotive. 4 locomotives of this class were built in 1915. They were all withdrawn in 1916 and rebuilt into P7sa class 4-4-2 locomotives. The locomotive carrying William's number, 110, was later scrapped.
William is painted green with brown lining. He has a brown running board and cowcatcher. He also has his number "110" and "P&RR" in brown on his cab and tender, respectively. He also has a navy blue smokebox and piston rods.