It went according to plan, except for killing an innocent man.
From the moment he left his appartment, Menezes was thought to be one of the 21st July attempted bombers. They could have arrested him at any time as he was tailed to Stockwell tube. But they let him get on train then killed him. Job done. Except it was a mistake.
But suppose they did in fact kill an associate of the bombers, what then?
Well of course no questions asked about unlawful killing, murder or infringement of "health and safety"
then it would have been Hero! Got you! Brave Cops risk lives to protect public...Grateful Nation Praises Armed Police Action
in fact just as it was designed to be
(no calls for a public enquiry then would there?)