The first ten locomotives were introduced in 1870 to replace 1849 built 4-2-2s. The last of the locomotives were withdrawn at the end of the broad gauge on 20 May 1892.
Three more locomotives were built in 1874. These were designed to be converted to standard gauge but this was never carried out, the locomotives all being withdrawn by 1886.
Reed, P. J. T. (February 1953). White, D. E. (ed.). The Locomotives of the Great Western Railway, Part 2: Broad Gauge. Kenilworth: RCTS. ISBN0-901115-32-0. OCLC650490992.{{cite book}}: CS1 maint: ignored ISBN errors (link)
Reed, P. J. T. (December 1956). White, D. E. (ed.). The Locomotives of the Great Western Railway, part three: Absorbed Engines, 1854-1921. RCTS. ISBN0-901115-33-9. OCLC12654357.{{cite book}}: CS1 maint: ignored ISBN errors (link)