When I was 14 I cycled from the top to the bottom (well, Llandudno Junction to the coast just past Bridgend).
We were riding mostly roads then, when we got to Mach, thought we’d take the trail to Nant-yr-Arian and rejoin the route there.
Needles to say, a raligh special and my old mans bike (which, if I was being trendy would describe as a CX bike…..but did they exist 14 years ago?) with panniers was not well suited to offroading so we headed back and ended up losing half a day.
Got a great sense of achievment out of it, especially being one of the ‘fat kids’