Earlier generations of Britons believed that certain things simply could not happen in Britain. Even in the country’s darkest moments of war or depression, this conviction differentiated the then proud nation from the U.S.S.R., third world countries, and unstable regimes that might fall to dictatorship any moment. News blackouts, and the banning of a book or film of course occurred here or there, but these never seemed very serious events. When the Thatcher government banned the sale of...