It was a superheated version of the LNWR Class G with 8 inch piston valves .
The London and North Western Railway ( LNWR ) Class G1 was a class of 0 - 8 - 0 steam locomotives .
Class G1 was a superheated class of the LNWR Class G with 8 inch piston valves .
The London and North Western Railway ( LNWR ) Class G1 was a class of 0 - 8 - 0 steam locomotives .