By Dominic Casciani
BBC News home affairs reporter
A few minutes after 1730 BST on 22 July 2005, an officer at New Scotland Yard wrote this in the operations log: "Person shot - Stockwell, Jean Charles Menezes, 7.1.78 Brazilian national."
The wrong man was dead and the fall-out was beginning.
Three years on, the inquest jury has rejected the police version of events that this was a lawful killing. They returned an open verdict and, in their answers, effectively criticised the police for what happened. We now know how Mr de Menezes died - the question is could it happen again?
Mr Menezes was caught on CCTV as he was followed by two officers
In July 2005 London was facing a unique and terrifying situation. Four bombers had blown themselves up on 7 July, killing 52. Four more had tried to follow them a fortnight later and failed.
The Metropolitan Police were not only trying to solve the first crime - they were now throwing everything they could into a huge manhunt following the second attempt.
Top detectives were lucky if they could snatch a few hours' sleep in the office. Police remember it as an operation like no other.
'Victim of circumstances'
Cressida Dick, the key police commander on the day, described to the inquest jury how she had managed the unfolding operation in a city on security lockdown.
Ultimately, she said, Mr de Menezes became a victim of "terrible and extraordinary" circumstances.
He had the misfortune to live in a block of flats detectives had linked to one of the bombers, Hussain Osman.
When the Brazilian left home, some officers thought he could be the suspect. But firearms teams were not on site in time to challenge him before he boarded a bus.
As he travelled through south London, mixed messages appeared to confirm, then reject and then confirm the view that he was the bomber.
Mr de Menezes' entirely innocent behaviour then appeared suspicious to some of the officers - although the jury questioned this account.
As Mr de Menezes approached Stockwell underground station, the need to stop him became crucial. Specialist armed officers from CO19 were told to intervene - and minutes later the 27-year-old was dead.
Deputy Assistant Commissioner John McDowall, in charge of the UK's counter-terrorism operations that day, told the inquest: "It is my belief that there was a mistaken identification and then there was doubt about whether that identification was correct or not.
"I think that was instrumental in bringing about the tragic outcome that we know of."
But speaking to the BBC, Maria Otone de Menezes, Jean Charles' mother, said many questions remained unanswered.
"Someone kills your son and comes and asks you for forgiveness. How would you forgive them? It's difficult.
"They're going to live the rest of their lives with the mistake they made weighing on their conscience. And I have to live the rest of my life suffering because I've lost an innocent son."
Giovanni de Silva, Jean Charles' brother, said he believed the Metropolitan Police were a "good police force", but added: "The point is that they made a serious mistake.
"I hope now that they change their behaviour, their training. Their image has become dirty with the family and with the world."
Planning and policy
At the heart of the 22 July operation were policies designed in the wake of 9/11 to confront suicide bombers.
It's people acting with the best of intentions - but of course the best of intentions don't always have the outcome that you want
Steve Swain, suicide bomber strategist, Metropolitan Police
The Met had envisaged two scenarios: an attack on a major public event or the appearance of a bomber on the streets.
The blueprint of how to handle the scenarios was known as Operation Kratos.
Officers were trained to creep up on an identified suicide bomber and then shoot him dead in the head with special ammunition.
The bullets used are hollow-point - meaning they spread on impact and are more likely to result in instant death.
But the order to kill can only happen once the officers are 100% sure that the target is a suicide bomber.
If the identification is not clear, the rules state they must challenge the suspect and see what happens.
Cressida Dick was the designated senior officer trained with overseeing a Kratos incident - but what happened on 22 July did not fit into either of the scenarios police had originally envisaged.
She told the inquest: "Looking for a failed suicide bomber was not something we had really thought about."
A key element of the suicide bomber strategy was the support of the armed officers on the ground with high-level intelligence gathered by operation room chiefs.
Surveillance officers who might be following a suspect, or assessing a crucial situation as it happened were part of this dependency network.
The inquest heard one of the shooters who leapt on to the train, C12, say that his undercover colleague Ivor had pointed out Mr de Menezes and said: "That's him".
C12 said those two words reinforced his understanding of what he was confronting.
He told the jury he shouted a warning, but Mr de Menezes stood up and approached his visible gun.
The words of identification and Mr de Menezes' alleged actions were followed by Ivor grabbing the electrician's arms and forcing him back into his chair. C12 and colleague C2 opened fire.
Returning their verdict, the jury at the inquest said they did not believe that warning was shouted. They sided with passengers who say they did not hear anything other than gunshots.
They concluded that Mr Menezes had stood up - but not moved towards the officer.
'Best of intentions'
Steve Swain, now retired from the force, designed the suicide bomber strategy.
He told the BBC that the officers' actions were consistent with their training.
Menezes family: Protest against inquest
"The surveillance officer pushing Mr de Menezes into the chair as he did, I think moved the firearms officers from 'I'm not sure' to 'I'm sure'," said Mr Swain.
"Grabbing him like that, [the armed officers must have thought] he must have some more information about that person than we have. And that's moved their mindset from 'I'm not sure', to 'I'm 100% sure'.
"It's people acting with the best of intentions. But of course the best of intentions don't always have the outcome that you want."
Nobody disputes that the officers feared they were following a suicide bomber.
But the family's case is that the firearms teams were not on a Kratos operation - and therefore the officers had not established whether the suspect genuinely posed "an immediate and mortal threat" when they pulled the trigger.
Based on this argument, they said the jury should have been allowed to consider an unlawful killing. The coroner disagreed on the grounds that there was insufficient evidence for a jury to say beyond a reasonable doubt that the officers acted illegally.
The law is quite clear that police can shoot to kill if they believe it is the only way to save innocent life. But the jury's conclusions on a number of key points indicate that they found the Met's operation had been fundamentally flawed.
The Metropolitan Police say there have been a lot of changes. Operation rooms have been completely redesigned and every conversation is recorded.
Police radios now work underground and surveillance officers have smartphones to receive updated suspect images while on the move.
The specialist firearms officers now receive more training - but in broad terms, the tactics for dealing with suicide bombers have evolved rather than fundamentally changed. They still use the same instant-death ammunition - and the "critical head shot" is at the core of the strategy.
The family have demanded a review of the entire saga - including decisions not to prosecute individual officers.
Police say they can't guarantee something like the Menezes killing will never happen again - and campaigners say this is reason enough to look again at every part of their suicide bomber strategy.
But senior police officers have not stopped apologising for what happened. The man who was at the top, Sir Ian Blair, has already quit.
So Cressida Dick's answer at the inquest, when she was asked if someone should be blamed, was unsurprising.
"I don't think so," she replied.