Cross country running? I can't be serious!

One of my achievements at CNS was not coming last in the first form cross country - I was 90th out if 91 - so why do I now have this urge to get my trainers on and head off to the nearest copse across some of the thickest mud since Monty Python and the Holy Grail? I can't really rationalise it beyond the attraction of the autumn colours and the desire to do as much active stuff as I can while the body still permits but it is real and I think I may have to do something about it.