A decision by the Parole Board to release the rapist John Worboys has been quashed, as the Board’s chairman Nick Hardwick resigns.
The legal challenge by two victims was upheld by the High Court which said “further inquiry” was needed into Worboys’ offending.
Worboys, 60, has served 10 years, including remand time, of an indeterminate prison sentence.
Mr Hardwick said he was resigning immediately.
In his letter of resignation, Mr Hardwick said Justice Secretary David Gauke had told him his position was “untenable”, adding he was “sorry for the mistakes that were made in this case”.
Responding to the High Court’s decision, the Parole Board praised the “bravery and determination” of the two women who brought the challenge.
The case will now be referred back to the Parole Board.
Worboys, who is now known as John Radford, was convicted of one rape, five sexual assaults, one attempted assault and 12 drugging charges – but police believe he committed crimes against more than 100 women between 2002 and 2008.
After a hearing about his case in November, the Parole Board decided to approve his release with “stringent” licence conditions, arguing its decision was based on appropriate evidence.
But the High Court judges said the Parole Board “should have undertaken further inquiry into the circumstances of his offending”.
Justice Secretary Mr Gauke congratulated the victims on the “unprecedented legal action” and announced plans to examine Parole Board rules, which could make the system more open.
London Mayor Sadiq Khan, who brought the challenge with the two victims, said the decision would bring “some reassurance to his victims and to all Londoners“.
At a court hearing this month, lawyers for Worboys’ victims and Mr Khan had argued that the former cab driver had been dishonest with the Parole Board and had crafted an account to convince the panel he was a changed man.
They said the “wider allegations” against Worboys should have been taken into account.
During his original trial, jurors heard Worboys – who became known as the black-cab rapist – picked up his victims in London’s West End and gave them champagne laced with sedatives, claiming he had won the lottery or had won money at casinos.