The Great Western Railway (GWR) 3600 Class was a class of 2-4-2T side tank steam locomotive. The Great Western Railway ( GWR) was a British railway company and a notable example of Civil engineering, linking London with the West In the Whyte notation for the classification of Steam locomotives by Wheel arrangement, a 2-4-2 has two Leading wheels four Driving A tank locomotive is a Steam locomotive that carries its own fuel and water on it instead of pulling it behind it in a tender. They gained the nickname "Birdcage" due to their spacious cab.