A police watchdog's decision to reopen investigations into three officers caught up in the "plebgate" row concerning Sutton Coldfield's MP is legally flawed and must be re-taken, the High Court has ruled.
The men are accused of giving a false account of a meeting with Andrew Mitchell MP during the high-profile dispute over whether he called Downing Street police "plebs" on September 19 2012.
Mr Mitchell, then chief whip, apologised for using bad language but denied using the word pleb. He later resigned as chief whip as the row continued.
Mr Mitchell held a meeting in his Sutton Coldfield constituency with Detective Sergeant Stuart Hinton, Inspector Ken MacKaill and Sergeant Chris Jones from the Police Federation in an attempt to smooth things over.
After the meeting the men, who represented officers in Warwickshire, West Mercia and West Midlands respectively, briefed the media.
Their account was questioned when a recording of the meeting was released.
The matter was referred to the Independent Police Complaints Commission (IPCC).
The watchdog body decided not to conduct its own investigation but to direct the police forces involved to investigate under IPCC supervision - West Mercia to investigate the case of Mr MacKaill, Warwickshire to investigate DS Hinton and West Midlands to probe Sgt Jones.
All three police authorities concluded the officers had "no case to answer".
Unhappy with the conclusion, Deborah Glass, then the IPCC's deputy chair, decided on October 30 2013 that the investigation into the officers' conduct should be turned into "an independent investigation" conducted by the IPCC itself.
All three officers applied to London's High Court for judicial review and, at a two-day hearing in July, asked two judges to quash the decision on the grounds that the IPCC had no power to re-determine the case.
Lord Justice Davis and Mr Justice Wilkie ruled that the IPCC did have power - but Ms Glass's decision must be quashed following allegations of apparent - though not actual - bias and a fresh decision taken.
Lord Justice Davis said the Plebgate incident had "gained notoriety", and the challenge was part of the "litigation aftermath".
In a scathing criticism of the police authority investigations, the judge said a series of misunderstandings and lack of a true appreciation of the requirements of the 2002 Police Reform Act and relevant regulations resulted in "a series of errors and irregularities that was simply lamentable".
The judge added: "I in fact would not disagree with the statement of the chair of the Home Office Committee when he described what happened here as seeming to be very much a 'car crash'.
"Nor would I disagree with previous statements of Ms Glass to the effect that there had been a catalogue of 'fundamental irregularities'."
The conclusions of the police authorities were so legally flawed that they were "invalid and of no effect".
The judge said the "most troublesome" issue before him were allegations that Ms Glass was guilty of apparent bias when she deciding to reopen the investigations.
As the IPCC's deputy chair, she had "publicly and repeatedly" made known her disagreement with the decisions of the police authorities.
Fairness meant that her decision must be quashed.
But the judge added it would be "utterly unacceptable" if the matter was left there.
He ruled that "the IPCC - with entirely fresh personnel in place - can properly be left to re-determine the matter", and also conduct any subsequent investigation thought necessary.
The judge observed that Ms Glass would no longer be involved. She is now in "a very senior public position in Australia".
An IPCC spokeswoman said: "We welcome the court's judgment that there was no proper final report prepared for this investigation and therefore the decisions of the three police forces that there wasn't a case to answer for any of the officers were invalid.
"This is in line with our own view. The IPCC will make a fresh assessment of whether or not to exercise its power to change the form of the investigation."