Sea Lion is a steam locomotive built in 1896 to supply the motive power to the Groudle Glen Railway on the Isle of Man and the locomotive still provides the main traction there today. The locomotive was built by W.G. Bagnall & Co., Stafford and delivered to the line in May of that year, providing sole motive power until joined in 1905 by sister locomotive Polar Bear. When delivered to the railway, the locomotive carried an olive green livery with vermilion and yellow lining and the name carried on the side water tank in gold leaf with blue shadowing, with distinctive round "spectacle" cab windows back and front. These were changed over to rectangular windows very early in the engine's career to improve driver visibility however. One distinctive feature was a displacement lubricator mounted atop the highly polished brass dome. The locomotive was fitted with unusual valve gear patented by E.E. Baguley and is one of only two locomotives to remain in existence with this (the other being Rishra on the Leighton Buzzard Narrow Gauge Railway). By the 1920 season the locomotive was deemed too costly for repair and the line purchased two battery electric locomotives that inherited their steam engine names. The modern engines proved to be financially disastrous and within a few years "Sea Lion" had been returned to the works for re-build.