From what I've seen and read today, there were many reasons to have had this family under surveillance. They all appear to have been involved in terrorist activities and 'training' for some time. Their friends and contacts were nearly all radicalised Muslims. Even ex-schoolmates and neighbours had their suspicions, and the Police had received information about them, yet nothing constructive was done.

It's unpleasant to be paranoid and report people one has doubts about, but in the present climate, it's essential.

How bitter the bereaved families must feel, knowing the bomber and his clan had been noticed quite a long time ago, and that this atrocity might have been prevented...