Scotland Yard has hit back after questions were raised about how long it took officers to reach the scene of the terrorist murder in Woolwich.
Assistant Commissioner Simon Byrne said that officers reached Artillery Place within nine minutes of the first 999 call telling them a man was being attacked.
It took 10 minutes for firearms officers to reach the scene after they were alerted to the presence of a gun.
He said: "I would like to address some of the speculation as to how long it took the Met to respond yesterday as this incident started to unfold.
"We first received a 999 call from the public at 2.20pm stating a man was being attacked, further 999 calls stated that the attackers were in possession of a gun. We had officers at the scene within nine minutes of receiving that first 999 call.
"Once that information about a gun or guns being present was known firearms officers were assigned at 2.24pm. Firearms officers were there and dealing with the incident 10 minutes after they were assigned, 14 minutes after the first call to the Met."
Eyewitnesses said that it had taken armed officers around 20 minutes to get to the scene of the attack.
Julia Wilders, 51, who lives near the scene, said she and her husband saw the victim being attacked, and then around 20 minutes later one of the attackers clutching two meat cleavers and charging at the police as they pulled up in a car.
This was echoed by a man identified only as James, who said he saw two black men chopping at a man in his 20s like he was "a piece of meat".
Conservative MP Robert Buckland told the Daily Telegraph it would be "very worrying" if armed officers had taken 20 minutes to arrive.
Mr Byrne called for calm as the investigation into the barbaric killing continues, following scuffles between members of the far right English Defence League and police in Woolwich last night.
He said: "The investigation into the shocking murder of a serving soldier yesterday is ongoing, and is of course a major investigation for us.
"It is only right that the ongoing investigations are allowed to take place, and they must take as long as is needed without anyone pre-empting what they may conclude. I would ask for Londoners' help and support for us to continue. Please remain calm. London is at its best when we all come together and now is the time to do that.
"There were small incidents of minor disorder in Woolwich last night, but these were closely monitored and dealt with, where appropriate, by officers in the area. There were no arrests or reports of any injuries or damage and there have been no further incidents reported."
He also repeated appeals for witnesses to send film clips and still photographs of what happened to woolwichmetincident.co.uk