After the leak of documents about the police shooting of Brazilian Jean Charles de Menezes, a row has broken out between the Independent Police Complaints Commission (IPCC) and Scotland Yard over the inquiry.
BBC News assesses what has been said - and finds many questions have been raised.
As if the investigation into the shooting of Jean Charles de Menezes was not a severe enough test for the IPCC, the leak of witness statements - whatever the source of the leak - presents an even greater challenge for an organisation anxious to establish its credibility.
The IPPC says Scotland Yard initially resisted its probe into Mr Menezes' death
The initial "rush to judgement" after the events of 22 July had died down, much to the relief of both the IPCC and the Metropolitan Police.
Now, speculation - based on what can only be a partial evidential picture - is dominating the headlines again.
Early comments made about the shooting by the Metropolitan Police Commissioner, Sir Ian Blair, are again being subjected to close scrutiny.
What he said was qualified by the phrase "as I understand the situation" and information was still being pieced together.
In one or two previous high-profile incidents when Met tactics have been called into question, the force, or its press officers, have presented an early version of what happened which was later undermined
But the Met did little, if anything, to disabuse the media of the notion that Mr Menezes was wearing a bulky jacket, had vaulted the ticket barrier at Stockwell, and had failed to obey a shouted instruction from officers to stop.
While it is true that much of this information came, originally, from witnesses at the scene rather than the police, the Met clearly had an interest in fostering this version of events.
In one or two previous high-profile incidents when Met tactics have been called into question, the force, or its press officers, have presented an early version of what happened which was later undermined. This may be another such case.
If the leaked information is accurate, there are many puzzling and vital questions.
If, as suggested, the strategy was to arrest anyone emerging from the Tulse Hill address as soon as possible and the Gold Commander instructed that the target was not to be allowed to enter the Tube, why did the eventual "hard stop", as it is known, take place underground?
At what point was a positive identification made, given that video surveillance was apparently compromised because an officer was attending a call of nature?
And, perhaps most critical of all, what decision-making process led to the fatal shooting if, as claimed, one officer had pinned Mr de Menezes in his seat?
As more potentially damning information leaks from the inquiry by the day, Sir Ian Blair has strenuously denied suggestions of a cover-up.
But his case has hardly been helped by the revelation that he sought to prevent the IPCC taking over the inquiry by enlisting the intervention of the Home Office.
Sir Ian Blair 's comments after the shooting have been scrutinised
Given that there is a statutory requirement for a police force to refer such a shooting to the IPCC, this appears to have been a tactical error and one which has clearly enraged the IPCC.
The statement from its deputy chair, John Wadham, that it "overcame" the Met's attempt to block it, securing "an important victory for our independence", smacks of an unsavoury power struggle between the two organisations and is likely to leave the public even more bemused.