The latest security measures imposed last week followed intelligence warnings that al Qaeda's chief bomb maker, Ibrahim Hassan al-Asiri, who is thought to be based in Yemen, had linked up with jihadists in Syria to pass on his skills.
I have no doubt, from what I have learnt, that these new steps are not bureaucratic nor an overreaction.
Sadly, they are unavoidable.
It is simply foolish to believe that the threat is either minimal or now behind us.
We have, indeed, been fortunate but, sadly, this has not been because the terrorists have, since 2005, given up trying to do us harm.
As Andrew Parker, the head of MI5, has made clear, each year there have been serious plots which if they had not been identified and disrupted would have led to the deaths and mutilation of many British citizens.
Sir Malcolm Rifkind, the chairman of the Intelligence and Security Committee, who disclosed that he had been briefed in advance about the measures, said that he had been left in no doubt that they were necessary.
However, he said that he had encountered a level of complacency among some elements of the public which he found "seriously disturbing".
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