by Ben McCarthy BBC Midlands correspondent

Brenda and Jeffrey Tanner were well known to social services in Cambridgeshire.

In the mid-1980s when a family they knew had problems, the Tanners agreed to foster their son on an unofficial basis.

The couple had no training in fostering children

The arrangement was made with the knowledge of social services.

They then fostered a teenage girl on an official basis.

For a period of about seven years, both children, who cannot be named for legal reasons, were subjected to a catalogue of abuse.

'Prisoner'

Jeffrey Tanner was found guilty of cruelty, unlawful wounding, assault, grievous bodily harm. At one stage he made the boy eat dog excrement.

If anyone had any idea about what was going on they kept their suspicions to themselves

He was described by the judge at King's Lynn Crown Court as depraved and cruel.

Although he was said to be the principal abuser, his wife Brenda Tanner was convicted of cruelty and grievous bodily harm.

Police first became involved in January 2000 when a woman in her late thirties, who has learning difficulties, claimed to have been held prisoner by the Tanners for almost a year.

That led police to others who had stayed at the house, and their investigation then centred on the children the Tanners had fostered.

Scruffy

All the violence happened at the family home on Gladstone Street in Peterborough.

Jeffrey Tanner was jailed for seven years for cruelty

The Tanners occupied three adjacent houses - part of a terrace. They are scruffy and the gardens are full of rubbish.

At first the police feared that there may have been other victims, and teams of officers began digging up the back garden searching for bodies - but no new evidence was revealed.

Gladstone Street is a busy place. The Tanners are well known, having been there for many years. But if anyone had any idea about what was going on they kept their suspicions to themselves.

Vulnerable

The couple had no training in fostering children.

Brenda Tanner was sentenced to 3.5 years

They already had five children of their own and the home was chaotic.

During the trial the court heard that the one thing the two foster children had in common was that they were both vulnerable.

They had learning difficulties and acute social and behavioural problems, having been abandoned by their own parents.

What they needed was care and support - what they got was abuse.