By Mark Easton Home editor, BBC News

The torture of the little girl in this case defies comprehension. But we still seek some kind of explanation, someone to blame, some lessons we can learn.

The girl's parents admitted three counts of child cruelty

Inevitably comparisons have been drawn between the plight of Child B and Victoria Climbie, whose appalling maltreatment and ghastly death prompted a complete rethink on the way we look after vulnerable children in this country.

There are echoes of the Climbie case, the most disturbing being that, just as with eight-year-old Victoria, the little four-year-old girl in Westminster wasn't taken aside and asked what she wanted.

No-one took her or her brother somewhere safe and private to find out how they felt about being returned to their parents.

If we are serious about putting the welfare of the child at the centre of our child protection system then this would seem to be a significant failing and there are obvious lessons to be learned.

Important difference

But to my mind there is one important difference between this recent case and that of Climbie. The Laming Report into little Victoria's death found systemic failure - agencies passing the buck and not communicating with each other.

Child B's case attracted far more official attention that that of Victoria Climbie

Lord Laming's report was scathing about the bureaucracy and called for major legal and structural change, much of which has now come about.

In the case of Child B, the independent inquiry board found something very different - "a significant amount of assessment activity undertaken by a range of professionals".

There was no lack of involvement, indeed the board noted that "there was hardly a period of time when the parents were not in receipt of some sort of assessment practice or were subject to observations".

While, with the benefit of hindsight, the board do draw attention to certain failures in the case of Child B, what really comes through in their report is what they describe as the "rule of optimism".

All the agencies were involved, they talked to each other, they took decisions together.

But when it came to the key meeting at which they had to decide whether Child B and her brother should live with their natural parents or go into care, as the board's report puts it, "more professional scepticism was needed".

As professionals they would have known that it is generally in a child's best interest to stay with their family if at all possible. It seems that on this occasion they so wanted that to be the case, the team of professionals convinced themselves everything would be fine.

The optimistic voices held sway.

Managing risks

As the board report puts it: "This case brings to the fore that child protection is about managing levels of risk, and that in doing so both the strengths and weakness of parenting abilities have to be rigorously and equally addressed."

It wasn't so much the failure of the system as a failure of judgment. The case of Child B is not an isolated one. Many children live with their parents even though the authorities know they are at risk.

The difficulty is in balancing the risk of keeping a child in a family against the risk in putting a child into care.

What Children's Services try to do is judge whether family situations in which there is an element of risk can be supported and helped to keep a child with its parents.