LONDON has been rocked by bombs exploding on the public transportation system. The old city has a long history of frightening terror attacks, but it also has a high degree of resilience. More than half a century ago, the generation of the 1940s saw Nazi bombers in the skies scattering bombs on military and civilian targets and the senseless attack of the V-2 rockets. Then, more recently, a wave of terror spread by the IRA lasted from the 19