Ivan Farrier is the chief engineer of the Arlesdale Railway.
After Rex's steampipe began leaking one day, Frank had to take his train, and the Small Controller began thinking that they needed another engine. So he arranged with Ivan Farrier for another locomotive to be built. Ivan Farrier then designed and helped build Jock.
He was the one who first revealed the secret plans to build Jock to Bert when the latter was awaiting new tubes to cure his loss of steam.
In 1985, Ivan Farrier and the volunteers of Arlesdale used spare parts to rebuild Blister I and Blister II with two 2-cylinder 12 h.p. He also replaced Sigrid of Arlesdale's Ford 4 cylinder engine, with a 6 cylinder Perkins from plans made by the Small Controller.