Matthew Byrne admitted five counts of sexual assault
The ex-boss of a Liverpool children's charity has been jailed indefinitely after admitting the "sadistic torture" of women in a string of sex attacks.
Matthew Byrne took prostitutes to his home in Wirral where he tied them up, beat them with a cane and suffocated them, Liverpool Crown Court heard.
Byrne, of Tollemache Street, New Brighton, Wirral, pleaded guilty to five counts of sexual assault in March.
He must serve at least three-and-a-half years before being eligible for parole.
Judge John Phipps imposed an indeterminate sentence for the public's protection.
He told him: "You subjected your victims to sadistic attacks of the most extreme kind.
"One of them said it was torture and that seems to me an apt description of what you did."
Byrne, who was a director of the Young Person's Advisory Service, also admitted four counts of possession of indecent images of children, involving about 9,000 images.
Peter Davies QC, for the prosecution, told the court Byrne would pick up the prostitutes and take them to his home where he had transformed a bedroom into a "torture chamber".
"This was a campaign of planned, deliberate and violent exploitation," the prosecutor said.
The court was told Byrne cruised Liverpool's red light districts, picking up prostitutes by appearing polite and pleasant and offering an "over the odds" payment.
Mr Davies added: "Each of these girls was vulnerable. They were all desperate for money to feed their addiction to drugs.
"As such they were easy prey to the temptation of easy money offered by an apparently articulate, well mannered and intelligent man who was intent on exploitation."
None of the women he attacked complained to the police, but two of them told their case worker who then informed officers.
Byrne was arrested on a separate matter last June, when CCTV on a train caught him taking pictures of school girls with his mobile phone.
A guard on the train alerted British Transport Police who questioned him and then searched his home, finding the torture equipment in the bedroom.
Merseyside Police were then alerted and detectives made the connection with the attacks on the prostitutes.
Byrne never directly worked with children involved in the Young Person's Advisory Service, the court was told.
The judge said he can only be released when the parole board is convinced he is no longer a danger to young girls or street workers.
He was ordered to sign the sex offenders register and made subject to a sexual offences prevention order which bans him from being in the company of young girls and street workers.