The police commander who launched the surveillance operation which ended in the death of Jean Charles de Menezes has told a court: "We did our best."
Commander John McDowell was 'gold commander' on 22 July
Commander John McDowell told an Old Bailey jury he thought constantly about what could have been done differently.
His team was working under "difficult circumstances" on the day the innocent Brazilian was shot, Mr McDowell said.
The Met Police denies breaking health and safety laws when it mistook Mr de Menezes for a suicide bomber in 2005.
Mr de Menezes, 27, was shot seven times by two firearms officers at Stockwell Tube station on 22 July 2005.
Mr McDowell was the "gold" commander who dispatched a surveillance team to Mr de Menezes' block of flats, believing failed 21 July suicide bomber Hussain Osman lived there.
The gold commander has overall responsibility for the strategy of a major operation. Below him are silver and bronze commanders who manage tactical and operational decisions respectively.
Mr McDowell told the trial on Wednesday: "I have since that time constantly thought about what other potential tactics or strategy might have been available to me because of the outcome of this tragic set of circumstances.
"I have done that on a weekly, if not daily, basis.
"I remain of the view that I and we did our best that morning to mitigate what was clearly a threat to the public in very difficult circumstances."
Clare Montgomery QC, prosecuting, asked why, despite Mr McDowell launching the operation at 4.55am, the firearms team had not been briefed and sent to the flats by the time Mr de Menezes left for work more than four hours later.
If they had been in place, the Brazilian could have been challenged before he had a chance to board the Tube, where officers were to stop him "at any cost", Ms Montgomery claimed.
Composite: Defence created image to show identification problems
Asked by Mr Justice Henriques if this four-hour delay was an "acceptable passage of time", Mr McDowell said it was the "quickest time that that team could be assembled and deployed with all the considerations that were bearing upon us that morning".
The judge then asked: "Could that have been done differently?"
Mr McDowell said: "With hindsight, it is entirely conceivable it could have been."
The Special Branch officer in charge of the surveillance teams, codenamed Alan, told the court the delay was "totally unacceptable".
The officer, who was an acting detective chief inspector at the time, was asked by Ronald Thwaites QC, defending, if there had been a "relaxed regime" about the need for teams to get to the flats.
"No, it was totally unacceptable," Alan said. "That was not my understanding.
"Commander McDowell wanted the resources deployed as soon as possible. That was clear. There was no relaxed regime. It was immediate, really."
The silver commander on the day, Det Supt Jon Boutcher, told the trial that without firearms support, none of the officers at the flats could have stopped a suicide bomber.
The judge asked him: "Was there anything or anybody there to prevent a genuine real bomber getting into the transport system?"
"At the location, no," Det Supt Boutcher replied.
Detective Chief Superintendent Timothy White, who gave authorisation the night before for firearms to be used to detain the suspected 21 July bombers, also gave evidence on Wednesday.
He told the court that the pursuit of the failed bombers was the most dangerous operation police had ever been involved in.
"We never faced a suicide bomber or a manhunt of this significance in police history," Det Ch Supt White said.
He was asked by the judge if there were circumstances under which the suspects might not be immediately arrested.
"With public safety paramount and the positive identification of a suicide bomber, we'd do our utmost to detain that person," he replied.
The case continues.