Graphic eye-witness accounts of the last seconds of the life of Jean Charles de Menezes, the Brazilian mistakenly shot by the police in July 2005, will be released to the public for the first time this week.
The release of the Independent Police Complaints Commission (IPCC) report is one of three hurdles the head of the Metropolitan Police, Sir Ian Blair, will have to clear in the next 12 days in order to keep his job.
Britain's most senior policeman is so far defying calls for his resignation since the Met was found guilty on Thursday of "fundamental failures" in the anti-terror operation that led to the 24-year-old Brazilian's death in a Tube carriage at Stockwell station the day after a failed bomb attack on London.
However, it appeared last night that Sir Ian could escape personal censure in the report, although it will criticise Commanders John McDowell and Cressida Dick, who ran the operation that led to the death of Mr de Menezes, according to a the News of the World.
The IPCC is believed to have suggested that prosecutors must consider if Commander Dick was "grossly negligent". It also reportedly concluded that Commander McDowell failed to brief colleagues properly.
Sir Ian could also face a vote of no confidence this week by the Met's political watchdog, the Metropolitan Police Authority. He must also appear before the Greater London Assembly.
The IPCC will tomorrow decide when to make its report into the incident public. Kept secret while legal action over the shooting took place, the report contains evidence that has not yet entered the public realm, an IPCC spokesman said.
"The report will fill in a lot of the gaps," he said. "The trial did not give a full picture in that certain witnesses were not called. It will give a clear idea of what happened on the Tube train itself."
The report sets out the law and will make recommendations for the future. It has already been considered by the Crown Prosecution Service, which decided there was insufficient evidence to charge individual officers. But details of Mr de Menezes' last moments – he is believed to have been shot seven times in the face – will reignite debate over the Met's handling of the case and make clear whether or not the 27-year-old electrician acted aggressively towards the police.
A key defence of the Met is that in the immediate aftermath of the 7 July bombings and the failed bomb plot of 21 July, the armed officers had to make a split-second life-or-death decision on whether Mr de Menezes – mistaken for a terrorist – was carrying a bomb.
The Met was fined £175,000 on Thursday, plus £385,000 costs, after it was convicted at the Old Bailey of exposing the public to unnecessary risk under health and safety law. Critics of Sir Ian Blair say he should take responsibility for the force's failings and what were described as 19 " catastrophic errors".
One former senior officer alleged that Sir Ian, 54, has lost all support among rank-and-file police and some senior officers. "He should quit," he said. "Blair is out of his depth... A member [of] the selection panel [when Sir Ian was chosen] said if you're faced with three lemons and a raspberry you go for the raspberry."
Sir Ian does have important backers, however. The Mayor of London, Ken Livingstone, is unswerving in his support, as is the Home Secretary, Jacqui Smith.
His supporters point out that the jury found that no individual should be held responsible for Mr de Menezes' death and that the failings were not " systemic".
Glen Smyth, Metropolitan Police Federation chief, said: "Sir Ian has not been treated fairly. It is nothing but naked political opportunism to seek his resignation."
Next in line? Contenders for Met's top job
Sir Hugh Orde
Chief Constable of Police Service of Northern Ireland. Former Met officer who helped develop race relations strategy. Has spent five years in Belfast.
Head of the British Transport Police and former Assistant Commissioner of the Met.
Sir Ronnie Flanagan
Her Majesty's Chief Inspector of Constabulary who advised on reforms to Iraqi police. Former Chief Constable of Royal Ulster Constabulary and its successor, the Police Service of Northern Ireland.
Chief Constable of Greater Manchester and former Met Assistant Commissioner, where he was in charge of policing the Notting Hill Carnival. A skilled media operator.