George Monbiot argued in an article, "How Britain became party to a crime that may have killed a million people," in The Guardian, January 1, 2008, that the U.K. needs a written constitution to keep it from going to war without a formal declaration by Parliament. A written constitution requiring a formal declaration of war didn't stop George W. Bush in the U.S.
What the U.K. needs is for every citizen to have the real law written on his and her heart.
Monbiot claims that the Empire forgets its mistakes of the past. However, the longer things drag on, the more it becomes apparent that they don't forget. They don't consider the events of the past mistakes. What they consider is that "might makes right," which that kind of might does not.