The inquiry into the racist murder of the black teenager Stephen Lawrence has exposed a shocking succession of errors and misjudgments by the officers investigating his death, starting from the night he was murdered in April 1993.

Officers on the scene were given detailed descriptions of the killers by Stephen's friend, Duwayne Brooks, but failed to act on them; house to house inquiries were patchy; a car full of laughing white youths which drove past the scene half an hour after the murder was not tracked down for a week; liaison with the family was, in the inquiry chairman's own words, "hopeless."

Stephen was murdered at a bus stop in south London

Meanwhile, five different officers appear to have thought themselves in charge. But the Met's embarrassment has deepened with the increasing seniority of officers in the witness box.

The first was former detective superintendent Ian Crampton, who, like most other senior officers in this case, is now retired. He led the investigation for the first four days, and made the first major admission - that arrests could have been made in that time (they in fact took place two weeks after Stephen's death).

Then there was Detective Superintendent Brian Weedon, who said he delayed arrests further because he was unsure of the legal basis on which they could be carried out - an astonishing admission for someone of his seniority.

But arguably the most humiliating time has been had by former Detective Chief Superintendent Roderick Barker, who conducted an internal review into the police investigation, and concluded that apart from a few peripheral errors, everything had been fine.

Met Commissioner Sir Paul Condon has defended the force

His report, the Barker review, formed the basis of the Met's stout defence of its record on this case for four years.

Last week, Mr Barker, a former head of the Flying Squad, was told by the inquiry's chairman, Sir William McPherson, that his review was "indefensible" and his testimony to the inquiry, in which he had tried to defend his findings, "unreliable " - a startling judgement on a man described by one lawyer as the "creme de la creme" of the Met.

Racial backlash

Officers have defended their corner, frequently by trying to deflect some of the criticism from themselves onto the Lawrence's solicitor, Imran Khan - accused of being obstructive and difficult with police from an early stage - and sometimes even onto the Lawrences themselves.

Stephen's parents have battled for justice for five years

Deputy Assistant Commissioner David Osland has stood by remarks he made last winter that officers accused of racism by the family might like to consider suing them.

Senior supervising officer William Ilsley said they failed to respond to his invitations to meet, and commented that "it takes two to tango".

The Met Police Commissioner Sir Paul Condon himself weighed in after the Easter break, complaining of the unnecessarily harsh questioning his officers were being subjected to, and saying it might set back community relations in London by years.

But it is the incriminating evidence of his own officers, rather than the undoubtedly withering approach of Michael Mansfield, which will have done the most harm.

Several have said they were unaware that the term "coloured" is offensive to black people - this includes someone holding the third highest rank in the Met, and an inspector formerly in charge of a racial incidents unit.

And several junior officers have broken ranks with their bosses by declaring they never thought Stephen Lawrence's murder was a racist killing at all.

Inquiry chairman Sir William McPherson has criticised the Met's review of the case

The public gallery, mostly black, occasionally erupts into jeers of disbelief, not out of disrespect for the proceedings, but simply, it seems, because they cannot believe their ears.

What will be the eventual outcome of it all? No doubt for many people the attendance of the five suspects is crucial for the inquiry to make a proper assessment of what happened.

But should they not appear - and that of course hangs in the balance - the airing of the facts of this tragic case will have been of vital importance, in showing how a force which for years stood so stoutly behind its efforts in fact got it so desperately wrong.