The critical breakthrough in the hunt for the London bombers came on Monday night in a police video viewing suite. Detectives involved in watching thousands of hours of film for glimpses of the terrorists had been given a "profile" based on a simple question posed for their guidance by senior officers. The question was: what would the terrorists look like? The answer was that they would be young men, probably in their 20s and 30s, and they would be carrying rucksacks. At 8pm on Monday, on footage from a camera at King's Cross station in central London, officers found images...