4-4-0 – Wikipedia

The Great Western Railway built its Bogie class saddle tanks for the South Devon Railway in 1849, and others for its own use during 1854 and 1855. Between 1851 and 1876, the South Devon Railway acquired a further six saddle tank classes, and the Vale of Neath Railway a further nine.

https://en.wikipedia.org/wiki/4-4-0