When considering a suitable subject for the Centenary challenge layout, constrained to the dimensions 2 metres by 45 cms, we decided to assume that the line that was proposed to terminate at Porth Dinllaen on the Llyn Peninsula in North Wales was actually built and would have needed a small motive power depot.
There is a strong case that the Cambrian Coast Line which terminates at Pwllheli could have been extended the 8 miles to Porth Dinllaen. There were a number of proposals so to do with an eye on a potential sea route to Ireland, including one from Brunel as early as the 1830s.
If it had have been built, the nature of the topography there would have required an approach through a tunnel to a new harbour and the only logical position for the MPD would be a site surrounded by walls to retain the unstable cliffs. It would have to be accessed under a road bridge close to where the mainline emerged from the tunnel.
This was confirmed by a site visit in June 2024 (when a very acceptable pint was consumed after a walk to the Ty Coch pub on the beach there which is only otherwise accessible by a private road).