There was an unidentified predator around, and I had an unrideable flat tire.
This part of Wales is pretty wild. Between me and the car park, there were two wild rivers, dense forest including 200ft Douglas-fir trees, thicket, standing water, and cliffs. There was an unidentified predator around; it was about to get dark; and I had an unrideable flat tire - no tools, no pump, no phone.
I knew there was an escape route further down but I had never used it. It turned out to be steep, rough, and fast, but I missed the hairpin turn-off at the bottom as I was concentrating on not going over the handlebars. By the time I realized it, I had continued pushing on foot as the track turned upward. It was dusk - I should have been in the car park by then but I was still miles away. I knew I had to make a decision as my noisy clicking Hope hub was echoing off the cliffs and announcing my presence to everything with ears - including any other big black cats. I got on the bike and rode it out of there as best I could with the tire flat and the wheel bouncing along on the rim.
Finally, I saw the visitor lights blinking through the trees as I approached from the intermittently moonlit and pitch-black trail. I was relieved that I'd been using good quality wheels if not appropriately as tough tires, and had remained uneaten. I later reported my sighting of some kind of panther to the trail centre, but strangely they haven't put this on their website (I wonder why!).