In reply to Andy Hardy:
Do they measure it to the top of the trig point? I seem to remember from the film "An Englishman who went up a hill and came down a mountain" that mountains are measured to the top of a permanent structure on the top, which would be the top of the trig, but that does seem a bit silly.
This story reminded me of this article, "A probabilistic approach to Munro bagging" which I enjoyed a few years ago.
http://www.hills-database.co.uk/probMunros.html