Fascinating thread. I remember the old horse well. His sudden improvement at that age is a joy. My main question in racing for many many years now is the reason horses improve, away from the obvious in the young and inexperienced. Almost every NH season you get at least one who soars for a few races and then subsides again, partly due to the handicapper, no doubt.
Did Pam always train on Dartmoor? Maybe a move of location or training routine set Mac Vidi on the rise? I suspect that many horses become disenamoured with racing and or training very quickly. Sometimes, someone or something comes into their lives which lights their enthusiasm for a while. Being able to roam Dartmoor each day might well count as one of those things. Access to open fields and close company is probably another factor that makes for happy horses.