A man known as the M25 rapist has died in jail while being considered for release.
Antoni Imiela, 63, was given seven life sentences in 2004 for a series of rapes across the Home Counties against victims as young as 10.
A Prison Service spokesman confirmed Imiela had died in custody at HMP Wakefield on Thursday.
"As with all deaths in custody, there will be an independent investigation by the Prisons and Probation Ombudsman," the spokesman added.
Imiela is believed to have died of natural causes and his death is not being treated as suspicious.
He had been referred for parole in January but a hearing was unlikely to take place within six months.
The railway worker, from Appledore near Ashford in Kent, carried out a spate of horrific assaults on women and girls he had never met.
He grabbed them and dragged them into a secluded area, threatening to kill them and hit them.
After his 2004 conviction, Imiela's DNA was put on a police database.
A cold case review into a sex attack that happened on Christmas Day 1987 found a match between Imiela and victim Sheila Jankowitz, who died in 2006.
He was jailed for 12 years at the Old Bailey in March 2012 after being found guilty of rape, indecent assault and another serious sex offence against Ms Jankowitz.
In January, a spokesman for the Parole Board confirmed the Ministry of Justice had referred Imiela's case for a parole review.
The review is "following the standard six-month process for all indeterminate sentence prisoners", the spokesman said.
It came a week after the decision to release black cab rapist John Worboys which is now the subject of a judicial review.