These locomotives were built by the Hunslet Engine Company between 1886 and 1904, and were designed and supplied specifically to work the many galleries of the quarry at Llanberis, North Wales.

After earlier experiences with vertical boilered De Winton locomotives, the quarry company decided they needed more powerful locomotives to run on heavier, double-headed rail in chaired track on its more intensively worked quarry galleries.

To improve transport of cut slate to the mills and waste to the slag tips, a standard locomotive design that was powerful, lightweight and had a short wheelbase was required.

They produced Dinorwic (works number 51 of 1870), which is a clear precursor to the Alice class.

[1] 11 locomotives of this class were built for the Dinorwic Slate Quarry, with all surviving into some form of preservation.