They were based on the 4200 Class which had been introduced by the Great Western Railway in 1910.

The 5205 series were of the same general design and 70 of the 5205 class were built, 5205-5274.

They retained the straight frames of the 4200s, but had outside steam pipes and 19" diameter cylinders so were slightly more powerful than their predecessors.

[1] Twenty more locomotives to the same general design were built from 1930.

Goliath In 2012, Hornby released models of the 5205 class in both BR black and GWR green.