The boss of MI5 has said he is "profoundly sorry" that the security service did not prevent the Manchester Arena terror attack.An inquiry found the bombing might have been prevented if MI5 had acted on key intelligence received in the months before the attack.Director general Ken McCallum also expressed regret that such intelligence was not obtained.

The boss of MI5 has said he is "profoundly sorry" that the security service did not prevent the Manchester Arena terror attack.An inquiry found the bombing might have been prevented if MI5 had acted on key intelligence received in the months before the attack.Director general Ken McCallum also expressed regret that such intelligence was not obtained.