The odds MI5 is working against

“As many as four of the NHS terror cell suspects were already known to security services, it emerged last night,” reports The Daily Mail this morning. This revelation is bound to set off a debate about whether MI5 has bungled or not. But before you jump to conclusions, consider what Fraser Nelson wrote after it became public that Sidique Khan had crossed MI5’s radar before 7/7: 

“When the next terrorist attack hits Britain (and everyone who assesses the risk speaks of ‘when’) the names of the attackers will probably be found on an MI5 database. If the service is doing its job properly, it will have logged every young person who visits a suspicious Pakistani camp. But tracking all these people is beyond the remit of a free country. The Stasi had one spy for every 167 East Germans. They could keep tabs on everyone. For MI5, the ratio is one for every 20,000.