The policemen who shot Jean Charles de Menezes believed him to be a suicide bomber and “an instant killing was the only option open to them”, an inquest heard yesterday.

Sir Michael Wright, the retired judge appointed as coroner for the inquest, said that the two officers — identified only as Charlie 2 and Charlie 12 — shot Mr de Menezes because they thought he was about to set off a bomb on a crowded train at Stockwell Tube station.

“They were convinced he was about to detonate a bomb and that unless he was prevented from so doing everybody present in that carriage was going to die,” the coroner said.

The firearms officers fired seven shots into Mr de Menezes's head from a range of between one and eight centimetres using 9mm hollow-point bullets. Another shot misfired and one more missed.

The cause of death was officially recorded as “severe disruption to the brain”.

The coroner gave the jury a flavour of the evidence they would hear later in the inquest when the two officers testified and faced questions in public for the first time.

The inquest, at Southwark Coroner's Court sitting at the Oval cricket ground, comes after two independent inquiries and an Old Bailey trial that have closely examined the shooting.

There has also been a well publicised campaign by friends and supporters of the de Menezes family, some of whom protested outside and attended the hearings.

The coroner told the jury of six women and five men that they should forget everything they had heard, seen or read about Mr de Menezes's death, resist the temptation to do “private research” on the internet and concentrate solely on the evidence they would hear.

The inquest, he added, was not a trial; there was neither defence nor prosecution but “a search for the truth”.

“This is a factfinding exercise. It is not a forum to determine culpability or compensation, still less to dispense punishment,” the coroner said.

The undisputed fact that Mr de Menezes, 27, a Brazilian working in London as an electrician, had no connection with terrorism was stated forcefully. The coroner said: “It must be stated at the outset of this inquest, with the greatest possible emphasis, that Mr de Menezes was in no way associated with bombs, explosions or any form of terrorism.”

The hearing began with a painstaking two-hour jury selection process. To ensure that they had no conflicts of interest, the potential jurors were shown a list of witnesses' names and photographs of 48 police officers who will remain anonymous.

In a lengthy opening statement, the coroner talked the jurors through the events leading up to the moment at 10.06am on July 22, 2005, when Mr de Menezes was killed. He reminded them that London was in an anxious state after the 7/7 suicide bombings and the events of the day before, July 21, when four terrorists attempted to replicate that outrage by attacking three Tube trains and a bus.

The bombs failed to detonate and a police manhunt began for the would-be bombers. A gym membership card found at the scene of one attack put detectives on the trail of Hussain Osman, who had an address in Scotia Road, Tulse Hill, South London.

Surveillance teams were deployed to the address overnight with a plan that specialist firearms units would follow to stop any terror suspect leaving the address, a block of flats.

Mr de Menezes was late for work when he left the building at 9.33am. He was followed as he made his way on foot and by bus to an Underground station.

Different surveillance officers recorded different views on whether or not the suspect was Osman. Mr de Menezes was variously described as “a white male”, “North African”, “possibly identical” to Osman, and having “Mongolian eyes”.

Around 9.46am, a Scotland Yard control room log noted: “Not identical male, surveillance team to withdraw.”

But the watchers were not withdrawn and continued to follow Mr de Menenzes as he got off a bus and then back on, because Brixton Underground station was closed, and eventually alighted at Stockwell.

The coroner said: “It does appear that by the time Mr de Menezes had actually reached Stockwell station no member of the surveillance team had identified him as Osman.

“But at New Scotland Yard there does appear to have been a perception that he had been positively identified as Osman.

“Commander [Cressida] Dick was deeply concerned that he should not be allowed to go down into the Underground system. She said that she wanted him 'stopped'.”

The firearms officers, who had been on duty since 7am, reached Stockwell station after Mr de Menezes had entered at 10am. A dozen of them ran in, vaulting the ticket barriers. They had been briefed that they would encounter suicide bombers with apparent links to the 7/7 gang and who were “deadly and determined” and “up for it”.

The court heard that Mr de Menezes would not have known what was happening when he was shot and that he died instantly.

The jury will be taken on a tour of sites relevant to the case today and will begin hearing evidence tomorrow.

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