Culdee was built at the Swiss Locomotive and Machine Works in Winterthur, Switzerland, and arrived on Sodor in time for the railway's inspection. In March 1900, he was the first to be used in the test runs on the Culdee Fell Railway. When Lord Harry was delivered in March 1962, Culdee left for overhaul instead of Shane Dooiney as he was the most run down of the two. He arrived back on Sodor in May 1963, which is where the first story of Mountain Engines begins.
Culdee is careful, cautious and friendly. He is filled with advice to give to the other engines. Culdee is the sensible one of the Mountain Railway. He and his coach, Catherine are a fine team, and favourites with passengers. But he does like a bit of excitement, and tells great stories about the other engines.
In Sudric, "Culdee" translates as "Companion of God". The real life origin of the term comes from members of Christian monastic and eremitical communities of Ireland, Scotland, and England in the Middle Ages who were called "Culdees", which means "client/companion of God".
Like the other Culdee Fell Railway engines, Culdee is equipped with a face at each end.