Police chief defends Menezes action

But Commander John McDowell said he still thinks every day about what could have been done differently. At the time police were trying their hardest to protect the public from a clear threat under "difficult circumstances", he told the Old Bailey.

Mr de Menezes, an innocent 27-year-old Brazilian, was shot seven times in the head by two firearms officers who believed he was a suicide bomber.

The Metropolitan Police is on trial over alleged health and safety breaches which it is claimed resulted in the shooting at Stockwell Tube station in south London on July 22 2005. The force denies the charge.

Mr McDowell was the "gold" commander who dispatched a surveillance team to the block of flats in Scotia Road, in south London, where they believed Hussain Osman, who had tried to launch a terrorist attack the previous day, was holed up.

The court has heard that despite the operation being launched at around 5am, firearms officers were still not at the address when Mr de Menezes left the flats for work more than four hours later.

Prosecutors claim that he and the public were exposed to risk by the fact that armed police were not there to challenge him and he was allowed on to two buses and a Tube train, where he was shot dead.

It is alleged that "catastrophic" failures in police planning led to Mr de Menezes death.

On Wednesday Mr McDowell told the court: "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."