The Lancashire and Yorkshire Railway class 8 was a four-cylinder 4-6-0 express passenger locomotive designed by George Hughes in 1908. These original locomotives were described as “poor performers” . They suffered coal consumption as high as 100 pounds per mile plus mechanical problems causing very poor reliability. Around the time of their construction, they were nicknamed "Dreadnoughts" on account of their large size, after the then-new Royal Navy battleship HMS Dreadnought.
As designed, they were fitted with a saturated boiler, slides valves and Joy valve gear. In 1919–20, fifteen were rebuilt with superheaters, piston valves, Walschaerts valve gear and slightly larger cylinders. The nominal tractive effort of the rebuilds was 28,879 lbf (128.46 kN) which made these engines for a time the most powerful in Great Britain until 1922 when the Gresley pacifics appeared. The rebuilt locomotives were reported to be "a good workmanlike engine" and "an engine thoroughly master of its work", although still with a coal consumption on the heavy side.
The relatively early withdrawal of most units must be considered in the context that the LMS inherited 393 different locomotive classes at Grouping, and LMS chairman Sir Josiah Stamp thought it desirable to reduce this to just 10 classes.