In reply to BusyLizzie:
I got totally lost on Bodmin Moor once (no, twice!) I was used to running the coast path where you just keep the sea in sight, follow the yellow brick road and normally you're OK (there was that time in the dark when I wasn't, but, moving on...). So off I went into the moor with no map, no compass, no water. I ran up Brown Willy from the Jamaica Inn by a meandering route and on the way back managed to go north at one point when I should have gone south. It all looked much the same in both directions. In all directions, actually. I only realised for sure that I had made a mistake when some distinctive two-bladed wind turbines came into view that I knew were way off from where I should have been. I ended up running about five miles more than I meant to, including a dispiriting final two along the A30.
I remember that it spooked me that I could have got it so wrong, and I always take a compass now.
I also use the OS map app, which is brilliant, but other times I have deliberately gone out onto the moor in the dark or fog and tried navigating by dead reckoning after memorising the OS map. That is fun, when it is warm and I know that the worst that can happen is a wet but safe night out.