*Millie is a light blue French narrow gauge well tank engine who helps run Sir Robert Norramby's Estate Railway at Ulfstead Castle.

Millie is a youthful, fun-loving, friendly engine who is full of spirit. When crossed, Millie can be quite fiery and is unafraid to stand up for herself, but she is also fair-minded and not particularly spiteful. That said, she will take it upon herself to teach an uppity engine a lesson, should she feel the need.

Having worked on the his Estate Railway for many years, Millie is very loyal to the Earl and her relationship to him is like that of a personal servant. They have fun together and are as close as any friends, but there is also a certain formality to their relationship. She always wants to do the best by the Earl and will defer to his judgement in all things, but when it comes to other engines, she has a mind of her own.

Millie is based on a 0-4-0 well tank No. 8069 Tabamar, built in 1911 by Borsig, and under contract from Decauville. After having participated to war effort, the engine had been in service in a quarry in Provence, then was the property of the "Établissements Ruvenshort et Humbert" at Villeneuve-la-Guyard, in Burgundy. And now Tabamar is preserved at the Chemin de fer des Chanteraines near Paris, France. In 1995, Tabamar visited the Ffestiniog Railway, where it served on drive-an-engine duty at Boston Lodge. Unlike her basis, Millie has a rear coal bunker, chain coupling hooks, and has been regauged from 1ft 11 5⁄8in to 2ft 3in.

Millie is painted French blue with white lining and brass fittings. She has a golden running board, boiler bands and wheel spokes. Her front buffer beam and the front of her cylinder blocks are painted red. Sir Robert Norramby's crest is painted on her cab sides, while her name is painted in white on the sides of her boiler. Her smokebox, funnel, frames and rods are a very dark purple colour, while her cab roof is plain black.*