The eight Dido class locomotives were 0-6-0ST broad gauge locomotives operated on the South Devon Railway and Cornwall Railway and associated other adjacent railways. They were designed for goods trains but were also used on passenger trains when required.

The Cornwall Railway was a 7 ft 1⁄4 in broad gauge railway from Plymouth in Devon to Falmouth in Cornwall, England, built in the second half of the nineteenth century. It was constantly beset with shortage of capital for the construction, and was eventually forced to sell its line to the dominant Great Western Railway.