I am not the only person shaking my head at the thought this man was issued a visitor's visa. A thorough investigation is called for:

The revelation of Abdulmutallab's background has confounded terror experts. Dr Magnus Ranstorp of the Center for Asymmetric Threat Studies at the Swedish National Defence College, said that the attempted bombing "didn't square".

"On the one hand, it seems he's been on the terror watch list but not on the no-fly list," he said. "That doesn't square because the American Department for Homeland Security has pretty stringent data-mining capability. I don't understand how he had a valid visa if he was known on the terror watch list.

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A source said Dr Mutallab was "devastated" at the news but also "surprised" his son had been allowed to travel after he had reported him to the authorities. Abdulmutallab had allegedly become noted for his extreme religious views when he was at the British International School in Togo, where he is said to have preached Islam to his friends.

An official briefing on the attack said the US had known for at least two years that the suspect could have terrorist ties. Abdulmutallab has been on a list that included people with known or suspected contacts or ties to a terrorist or terrorist organisation. The list is maintained by the US National Counterterrorism Center and includes about 550,000 names.