Neil is a dark green tank engine with an unusual box shape and a Scottish accent. He is a simple but kind engine, who befriended Skarloey when he was young.
Built at the Neilson and Company Works in Glasgow, Scotland in 1856, Neil was part of the Sodor and Mainland Railway and helped to ferry Skarloey from the port of Kirk Ronan to his home at the Skarloey Railway terminus of Crovan's Gate. Very little is known about Neil, or what happened to him following the amalgamation of the S&M with the other railways on Sodor to become the North Western Railway. While it is possible he was scrapped, Sodor: Reading Between the Lines implies this may not be the case, describing him as "a survivor from the Sodor and Mainland Railway".
Skarloey said Neil was "ugly but kind", and they soon became friends.
Neil is based on a Neilson 0-4-0 box tank, a simple and robust class of engine built in Glasgow and sold all over the world. This basis is reflected in his name and class. His country of origin also explains his accent.
Neil is painted dark green with "S & M 2" written on his tank sides in yellow.