Victims of black cab rapist John Worboys believe something went "badly wrong" with a Parole Board decision to free him from prison, leading judges have heard.
The two women, referred to only as DSD and NBV, are bringing a landmark legal challenge at the High Court in London in a bid to block the serial sex attacker's release.
Outlining their case on Tuesday, their barrister Phillippa Kaufmann QC told the court: "Had it not been for the claimants' action in bringing this claim - the first time that victims have ever done so - the errors in the board's decision would never have been discovered."
She added: "It is submitted this is a case where the parole process has gone badly wrong."
Worboys, 60, who now goes by the name John Radford, watched proceedings via video from prison.
He was jailed indefinitely in 2009 with a minimum term of eight years after being found guilty of 19 offences, including rape, sexual assault and drugging, committed against 12 victims.
He became known as the black cab rapist after attacking victims in his hackney carriage.
Police believe he committed crimes against 105 women between 2002 and 2008 when he was caught.
But Ms Kaufmann told the court Worboys denied committing offences other than the ones he was convicted of and he said the "trigger" for his offending was the breakdown of his relationship in 2005.
Arguing the decision to release him should be quashed, she said the board excluded "critical evidence" which undermined his version of events when considering him for parole.
The barrister said this included the fact he was caught with a "rape kit" which included sleeping tablets, condoms and a vibrator.
The court also heard Worboys settled a civil claim brought against him by 11 women - some of whom made allegations for which he was not prosecuted - for £241,000 in 2013.
He received legal assistance with that case from serial killer Levi Bellfield, who he met in prison.
Ms Kaufmann said the Parole Board's reasons for believing Worboys no longer poses a risk to society included that he had "learned to be open and honest".
She said the board also considered his risk was reduced because of the fact he took "full responsibility" for his crimes, had "good insight" into his behaviour and had undergone treatment.
The court heard the material considered by the Parole Board when it reached its decision included the judge's sentencing remarks from Worboys' trial, but not a summary of the prosecution's case against him.
The Mayor of London Sadiq Khan and The Sun newspaper are also taking part in the legal action.
A temporary bar on Worboys's release, initially imposed in January by the High Court, is continuing pending the outcome of the proceedings.
Worboys, who has served 10 years behind bars including remand time, is represented at the hearing by Edward Fitzgerald QC.
Mr Fitzgerald will argue that the Parole Board did not have to take the "unproven allegations" against Worboys into account when reaching its decision.
The hearing before Sir Brian Leveson, Mr Justice Garnham and Mr Justice Jay will continue on Wednesday.