Kate the people making the "cock up" not cathing right guy. are professionals who are paid to ensure that the 'right' guy is caught. It matters not that they are parents etc, it is their job to ensure the safety of the public, and from what is appearing in the papers, it appears they did 'cock up', by not stopping this man when they had the chance.
I understand that there is a hang over in Germany from both the Nazi regime and the Stasi, about the state knowing too much, but to have no CCTV is negligent, and it seems like there is back tracking going on,. just as there was with Cologne.
The police and security services need to be lucky all the time; the terrorists need to be lucky once. I would suggest therefore that the Germans have to barter some freedom for security to give the security services a fighting chance to avoid deadly cock ups like this one.