For all he might have tried, every time a game was released with Lord British in it, players would figure out ways around the code and put him in the ground. With nine Ultima games and the more well-known Ultima Online incarnation, Lord British has bitten the dust more than a few times. Many of people never played the original Ultima series or weren't there when the infamous fire spell blasted Lord British face-first into the ground.
It's for this reason the you'll probably want to check out an article by CVG chronicling the many different deaths of Lord British. They even cover the way in which General British was killed during the beta for Tabula Rasa.