The Metropolitan Police have lost their Supreme Court challenge over a ruling which led to two women who were sexually assaulted by London cabbie John Worboys winning compensation.
The case was pursued to establish legal principles for the future and the women - only identified as DSD and NBV - were never at risk of losing their damages.
Lawyers for the Met, backed by the Home Office, said that imposing a duty of care on officers in relation to their investigations would have an adverse impact on operational effectiveness.
But on Wednesday, five justices unanimously dismissed the appeal.
DSD and NBV - who brought their claims under Article 3 of the Human Rights Act which relates to inhuman or degrading treatment - were awarded £22,250 and £19,000 respectively after the High Court ruled that the Met were liable to them for failures in its investigation.
Between 2002 and 2008, Worboys, who was jailed for life in 2009, carried out more than 100 rapes and sexual assaults using alcohol and drugs to stupefy his victims.
He remains in prison pending next month's High Court hearing into the Parole Board's decision to release him.