I don`t think anyone thinks that "the best way to deal with terrorists is to let them commit an atrocity first" You,me or anyone could get in car or Van or even hijack a lorry and plough into a crowded area killing many. The police cannot stop this sort of atrocity, however swiftly killing...
The best way to deal with terrorist is as the police did last night.....They can`t do it again and will not cost taxpayer anything in court or prison costs.