Nancy is a conductor's daughter who lives near the Skarloey Railway and occasionally polished the engines.

Born in 1953 to a guard and his wife, Nancy is distantly related to Mr. Percival, the Thin Controller, for she is the great-granddaughter of Beatrice, one of his sisters.

In Episode 17 (entitled Gallant Old Engine), she polishes Skarloey for Rheneas' return and Duncan became extremely jealous after she had no time to clean him, as she was scheduled to help the Refreshment Lady. In Episode 20 (entitled Very Old Engines), she polishes Skarloey for his centenary. After he becomes cross and she calls him a "crosspatch", Skarloey told her the story of his first days on the railway and the time he really was a crosspatch.

While not in any books after Books 17 and 20, it is believed that she has now grown up and lives with her husband, whom she met while he was working as a volunteer on the Railway, on the Isle of Man. They make the short journey back to Sodor to see their married daughters and the railway as often as they can.

Your lines will be highlighted in yellow when you receive your scripts. Your first episode will be Episode 17, at the beginning of the story entitled "Passengers and Polish." Your second and final appearance will be in Episode 20, at the beginning of the story entitled "Crosspatch."