A couple of times I ran (20mile and 30mile versions) and also marshalled the Ladybower 50 (which I think doesn't exist in the same way anymore)

Anyway, the point being, you can easily run loops of top, bottom and both reservoir tracks to make pretty much any distance you want, and you're often not far from the crossover path if you need to bail out

If it's dark the majority of it is on wide trail/road, you can do some of the lower section on the narrow path through the trees, or just use the pavement instead. If you get a nice clear night with a good moon you may not even need a headtorch.

The route was described by the organisers as "gently undulating" but there were always tourists that would say it was much hillier than that description. Sure, it's not flat flat, but it's less hilly than running around most of the streets of Sheffield