A religious tyrant who tortured his children in a campaign of "pure cruelty" may never be freed.

The fanatical preacher and his devoutly Christian wife were locked up after they were convicted of wounding and cruelty.

Judge Christopher Prince warned them both to expect substantial custodial sentences.

He said the father could be jailed for ten years, but he added: "He could receive an indeterminate period of custody which means he would not be released until the parole board are sure he is not a risk to members of society."

The couple who originate from Nigeria, who cannot be named for legal reasons, also face deportation.

Judge Prince told the man: "When you gave evidence you said you would not have treated your children this way because to do so would be pure cruelty. In that, you were absolutely right.

"You breached the position of trust parents have to their children and you engaged in a long campaign of pure cruelty - what has been described by your own counsel as torture of your children.

"It is not just the pain and injury you inflicted upon them in your care. There were also periods in between when they must have lived in fear of coming under your gaze and under your hand with the instruments you used to cause so much pain to them."

The judge told the boys' mother: "You must expect a substantial period of imprisonment. Children are entitled to expect to be protected by their parents, particularly from ongoing torture such as that administered by your husband. You made a conscious decision not to protect your children from that."

During the trial at Bradford Crown Court, the jury heard harrowing evidence from the couple's two sons.

They told how they were mutilated, bound and beaten at their Bradford home.

The boys, only seven and nine when the torture began, had safety pins fastened through their lips, their mouths were sliced with scalpel blades the older boy's tongue was pressed with sharp pincers.

They had clothes pegs clipped on their tongues and the younger lad was struck with a steel rod.

The older child was locked in a dark cupboard with his legs bound with wires and his eyes and mouth tied with a towel.

The man's wife turned a blind eye to the mutilation of her sons. She was convicted of two charges of cruelty.

Her barrister John Lucas said she lived with "a tyrant of a man who has scared her to four corners of her home".

The jury saw video clips of long family prayer meetings. The man preaches passionately, crying: "Remove the devil that has made them not listen."

He shouts: "God will seize this tongue. God will seize it."

The Crown alleged the former medical student might have mutilated the boys as his interpretation of religious teaching.

He told the children God had his tongue cut off in the Bible.

The judge agreed to probation reports on the Nigerian man, 47, and his wife, 41, before they are sentenced in March.

He approved the preparation of a psychiatric report on the man, who was convicted of 11 charges of cruelty and wounding.

Prosecutor Alex Taylor said the couple might be deported.

"That is a matter being actively explored at the moment," he told the judge.

The man's barrister Latiff Adenekan said police had his passport and there was no way he would abscond.

Mr Lucas appealed for the boys' mother to be allowed bail. He said she was a broken woman. Her children were in care and she was herself a victim.

The woman, characterised by the smart hats she was allowed to wear in court, was found guilty of cruelty to her sons by failing to prevent the insertion, or to remove, the safety pins from their mouths.

She also failed on several occasions to remove her children from harmful situations.

The couple came to Bradford from Austria in 2003.

The offences continued for 17 months until a learning mentor at the older boy's Bradford primary school saw bruising on his back.

A paediatric doctor examined the children and they were taken into care.

After the verdicts, the head of West Yorkshire Police's Child and Public Protection Unit, Detective Chief Inspector Stan Bates, said the degree of cruelty displayed was incomprehensible to most people.

He said: "The judge, quite rightly, described this as systematic torture. Every child has a right to feel safe. They should have felt safe at home with their parents."

Det Chief Insp Bates said the guilty verdicts were a positive result for the boys, who had been courageous in coming forward.

But he said it would take them some time to get over what had happened to them.

He added: "Our priority is to do all we can to safeguard and protect children living in our communities. I hope this case, and the outcome at court, goes some way to raising awareness about child abuse and the variety of forms it can take.

"This has been an isolated case. It is believed the motive for this abuse was an extreme religious belief. The police are increasingly working with faith groups and the community to raise awareness around child abuse.

"We are not in the business of challenging or policing religious beliefs. Our priority is to protect children and prevent them being victims of cruelty."