An elderly male separated from his wife and subsequently benighted. She returned to their hotel and reported him missing. A hasty search was organised around the Alcock Tarn area, and he was located, sitting in the dark, waiting patiently for rescue... He was assisted off the hill and returned to his hotel, wife and hopefully, dinner...
What ever time of year, always carry a torch. You never know when or why you may be delayed.
When it goes dark in the hills, it usually goes VERY dark! There's little ambient light unless you are lucky to be out when there is a good moon and little cloud.
It's worth carry a set of spare batteries as well. If you're lucky they'll be the same size as other devices you might be carrying such as GPS.
Modern LED torches are very reliable, and batteries last a long time, and it's well worth considering a headtorch in favour of a hand torch, leaving your hands free.