GWR Mercury Class
Design and development
Following the success of the Firefly orders, Gooch placed contracts in 1839 for a parallel class of slightly larger 2-2-2 express engines. The Mercury class shared the Firefly's general layout but had a longer wheelbase and slightly larger boiler, intended for the heavier expresses on the GWR's growing main line. 22 engines were built between 1839 and 1841 by various contractors.
Service and withdrawals
The Mercury class worked GWR express services from 1839 onwards, alongside and progressively replacing the older Star class. The engines were rebuilt with larger boilers in the late 1860s and most lasted until the abolition of the broad gauge in 1892. None of the originals were preserved.
Identification features
Broad-gauge 2-2-2, similar in layout to Firefly but with longer wheelbase. GWR holly green with brass and copper details.
Notable locomotives
- Mercury, Mars, Apollo, Venus, Hermes (1839–41, not preserved)