On a recent trip to Scotland, I had the pleasure of taking a tour at the Dewar's Distillery in Aberfeldy. It was built by John and Tommy Dewar in 1898 and is a great place to visit. The heritage tour begins in the old malting barn where you can spend as much time as you wish exploring the history of Dewar's. The guided distillery tour then takes you through the whole craft of making whisky, from milling, mashing and fermentation and into the Still House for distillation, and finally maturation. According to our tour guide (who was very good indeed) Scottish law requires that spirit must be stored for a minimum of three years before it can be sold as Scotch Whisky. At the Aberfeldy Dewar's distillery they allow their whisky to mature for a much longer period. They offer a Single Malt Whisky at 12 and 21 years old - both absolutely excellent and highly recommended.
There was a little mystery attached to the spirit because as it matured in the casks almost 2% "disappeared" every year. There were lots of suggestions as to who were the culprits but it was later determined the spirit merely evaporated and therefore was given the delightful term "the angel's share".