L&YR Hughes A Class

The Lancashire and Yorkshire Railway Hughes A Class was a series of four-cylinder 4-6-0 express passenger locomotives designed by George Hughes and built at Horwich Works from 1908, representing the most ambitious express passenger design produced for the L&YR and Hughes's most technically sophisticated locomotive type. The Hughes A Class was unusual in British practice for using four cylinders in a compound arrangement — two high-pressure outside cylinders and two low-pressure inside cylinders — drawing on French compound locomotive practice that Hughes had studied during visits to the Continent.

Hughes believed that compounding — expanding the steam first through smaller high-pressure cylinders and then through larger low-pressure cylinders to extract more work from the same steam — offered genuine efficiency advantages on the long-distance express working of the L&YR's Manchester–Liverpool and cross-Pennine express services. The A Class was his practical attempt to demonstrate this on the L&YR's principal express duties.

In service the A Class proved disappointing. The compound arrangement, while theoretically sound, was complex to operate and difficult to maintain at the L&YR's depots, which were accustomed to simpler inside-cylinder types. The efficiency advantages of compounding were offset by the higher maintenance costs and the greater skill required of the crews. The locomotives were never converted to simple expansion as the Midland Compounds had been developed. Hughes subsequently abandoned compound practice and his later L&YR and LMS designs used simple expansion. None was preserved.