Britain's most senior public order police officer apologised to MPs today after giving them false information when he denied having plain-clothes officers in the crowd at the G20 demonstrations two years ago.
Commander Bob Broadhurst said the information was "true to the best of my knowledge at the time" but it has since emerged that both plain-clothes and covert officers were deployed during the protests.
Giving evidence to MPs a month after the protests, in which thousands of demonstrators clashed with police in London in 2009, the senior Scotland Yard officer insisted there were no plain-clothes officers among the crowd, saying it would have been too dangerous to do so.
But questions arose about his evidence in the wake of the unmasking of undercover officer Mark Kennedy, who attended many demonstrations during seven years living as a spy among green activists.
Mr Broadhurst's admission raised questions over how the so-called gold commander in charge of the protests could be unaware that covert officers from his own force were being used.
Mr Broadhurst was also unaware that plain-clothes officers from the City of London Police were deployed at observation posts.
But Metropolitan Police Acting Commissioner Tim Godwin, who also apologised to the MPs, defended his commander's actions, blaming the large scale of the operation and saying inquiries into what went wrong were under way.
Last week, the Met issued a statement correcting the testimony given by Mr Broadhurst on May 19, 2009.
He told MPs then: "We had no plain-clothes officers deployed within the crowd. It would have been dangerous for them to put plain-clothes officers in a crowd like that.
"The only officers we deploy for intelligence purposes at public order are forward intelligence team officers who are wearing full police uniforms with a yellow jacket with blue shoulders. There were no plain-clothes officers deployed at all."
But this month's statement conceded: "Having made thorough checks on the back of recent media reporting we have now established that covert officers were deployed during the G20 protests.
"Therefore the information that was given by Commander Bob Broadhurst to the Home Affairs Select Committee (Hasc) saying that 'We had no plain-clothes officers deployed within the crowd' was not accurate...
"The officers were covertly deployed by the MPS (Metropolitan Police Service) to G20 protests to identify individuals who may be involved in the organisation of criminal activity and to give live time intelligence/evidence as to the protesters' activity."
But the Met stood by Commissioner Sir Paul Stephenson's assurance to the committee at the same hearing that the force did not use "agents provocateurs" - undercover officers actively fomenting unrest - at the protests around the world leaders' summit in April 2009.
The Met statement went on: "Prior to the evidence session, there had been extensive discussion in the media and then at parliamentary committees about allegations that police officers were acting as agent provocateurs in the protests.
"Such behaviour goes completely against how the MPS deploys officers. The commissioner's comments at Hasc refer to this point - not to covert deployments."
Sir Paul told the committee at the initial hearing that "the idea that we would put agents provocateurs in the crowd is wholly antithetic to everything I have known about policing for the best part of 34 years".
Today, Mr Godwin said: "When you actually run a huge operation on the scale Commander Broadhurst was running, you can't know everything all the time.
"And equally, the intelligence don't always know the source.
"However, I think what this has done is given us a sharp lesson and we will look at that."
He added: "With 55,000 people, 750,000 crimes, I can't always say that someone won't make a mistake. and equally I can't always say that commanders will know what every single member of our staff are doing."
Giving evidence to the committee, Mr Godwin went on: "The vast majority of men and women who fulfil this function on behalf of the police service are some of the bravest people that we actually have, and they have lots of controls... in terms of governance and oversight.
"Every now and then, things go wrong and we need to investigate those, and we need to find out what's occurred, but the vast majority do a splendid job for this country."
Asked about the deployment of covert officers on large-scale operations in general, Mr Godwin said their use "was not an exception at all".
Mr Broadhurst told the MPs: "May I first of all apologise.
"When I appeared before you on May 19 2009, I gave you some information that now appears to be inaccurate. For that, I apologise, but at the time I made it it was true to the best of my knowledge, otherwise I certainly would not have said it at the time."
The large-scale operation included deploying just under 12,000 officer shifts over five days protecting 46 people, including United States President Barack Obama on his first visit outside of North America, Mr Broadhurst said.
It was described at the time as the biggest peacetime operation the Met had ever undertaken, he said.
Mr Broadhurst said: "I hadn't asked for covert policing at any of those protests and wasn't aware that I had any."
Asked by committee chairman Keith Vaz if he should have known, Mr Broadhurst said: "There is a review going on into that, sir.
"I would always have a specialist working with me on intelligence.
"Normally they would tell me. It didn't happen on this occasion, hence I need to find out why that happened.
"It may well be, as you said, I didn't ask the right questions. Genuinely I did not know."
Mr Broadhurst went on: "There are inherent dangers of putting covert officers into many situations, but also crowd situations, and one of my concerns about not knowing is I wouldn't be able to help them and go to their assistance if I didn't know they were there.
"These are some of the issues we need to look at and make sure we put right for the future."
Asked if the Met commissioner should also have known about the use of covert officers during the G20 protests, Mr Broadhurst said: "No sir. It's my operation. I should have known, I didn't and I've apologised."
Mr Godwin added that Scotland Yard had looked at how widespread the media coverage of Mr Broadhurst's evidence was to ascertain whether anyone in the Met who knew about the use of covert officers should have seen his original statement to MPs and said something earlier.