Cefn Ddu was built by Nigel Matthews as an attempt to complete a model railway layout after a long absence from the hobby. The name Cefn Ddu means Black Ridge. Built to 009 standards, the layout is compact – in theory to make completion more achievable – and to fit into available space at home, actually an old wooden suitcase with internal dimensions of 24″ x 13.5″ (620 x 345mm)!

Cefn Ddu is based on the internal quarry workings of a North Wales slate quarry not unlike the ones at Dinorwic and Penrhyn. However, despite much of the rolling stock being based on these two quarries it is not a representation of either but a smaller freelance quarry. The quarry like its larger neighbours runs a nominal two foot gauge internal narrow gauge railway system for transporting raw and finished materials. The model represents the lower level of the quarry with slate slabs being delivered to the cutting shed, return workings with finished slate and also rubbish (off cuts of slate) pass in the opposite direction to sorting sidings off stage.

The scene is not set in any particular time period but is certainly before the industry‘s decline.