Security agency MI5 has warned that one of London’s most famous landmarks, the clock-tower of the Houses of Parliament known as Big Ben, is vulnerable to terrorist attack and has called for the area to be surrounded by a steel barrier, newspapers said. The 316-foot (96-meter) tower could collapse onto the parliament if it were structurally damaged, the report said. The tower, which takes its name from the 13.5-tonne hour bell, stood throughout the German bombing blitz in World War II, although the parliamentary chamber was hit by a bomb and destroyed. According to the reports, MI5 warned that the tower’s proximity to a busy road, and the fact it has been climbed by Greenpeace protestors indicated that it was at risk. The classifieid security survey also said the tower could be hit by the heavy concrete blocks designed to keep suicide bombers away from the parliament in the event of a large explosion. Full Story