Three weeks before the London bombings of July 7, Britain’s Joint Terrorist Analysis Center advised policymakers that ‘‘at present there is not a group with both the current intent and the capability to attack the UK.’’ That reassuring message from the country’s top intelligence and law enforcement officials, The New York Times reported last week, prompted the British government to lower its terror alert. Less than a month later, 52 people were murdered and 700 wounded when three subway trains and a bus were blown up. This latest example of a serious intelligence failure raises questions not only for London but for us, too: Which kind of intelligence failure is better — the kind that badly understates a threat, such as the one in London, or the kind that overstates a threat, such as the insistent warnings before the invasion of Iraq that Saddam Hussein was armed with weapons of mass destruction? Full Story