Every time Alyson Leslie finishes an investigation into abused children, she vows to never start another.

But something compels her to carry on.

She said: "This case was particularly draining because it involved the death of a child and everything which lay before him being cut off.

"During every one of these investigations I have sat down and wept. It is a luxury I have to allow myself, particularly when I think of my happy nieces and nephews.

"I then have to put these feelings aside and bring clarity to confusion. It is something which I feel I owe the child and it makes me carry on."

Ms Leslie spent almost a year investigating why the care system failed John Smith.

Her report is more than 100 pages and includes interviews with everyone involved in the boy's care. It suggests scores of specific recommendations to stop the tragedy happening again.

The report, required under The Children's Act, will be sent to the Department of Health which is not bound to follow any recommendations.

Despite this, Ms Leslie's criticisms have already led to changes in the city's adoption service.

She said: "The report has not been sitting on a shelf. Officers have been constantly in touch with me about what improvements they can make. I was very impressed with that."

With several huge investigations under her belt, Ms Leslie, a former assistant director of social services, is often called upon by local authorities in crisis to find out what went wrong.

Her credentials for the job are impeccable.

As a social worker in Scotland, she regularly dealt with children from horrendous backgrounds. Later, she examined management structures monitoring staff workload and standards.

While working in Fife, her department was subject to a three-year inquiry, costing millions of pounds. The investigation into efforts to reduce the number of children in care came to no conclusions.

Ms Leslie said: "It was an absolute waste of time. I found the whole process frustrating and began to look at better ways of handling inquiries."

Her work was recognised by the Scottish Office, which asked her to set up guidelines of how to send an inspection team into a local authority.

In 1993, she was appointed by the City of Newcastle on to a panel to investigate the Jason Dabbs case.

Dabbs was a trainee nursery teacher who systematically abused dozens of children in his care.

Ms Leslie and her colleagues examined how he had got on the training course and what went wrong.

She said: "No one had appreciated the scale of the problem. We ended up interviewing every child in two classes.

"Everyone thought something terrible had gone wrong but the teachers had behaved entirely professionally. Dabbs built up a bond with the children who willingly kept their secret.

"The divisiveness and artfulness of people who abuse children and the lengths they will go to means even the most caring, skilled and vigilant professionals can be duped."

Ms Leslie believes her role is to find the truth, not to assign blame.

She said: "We ask social workers on our behalf to do work we don't want to deal with.

" Cases like this bring us face-to-face with the often nasty reality there are adults who commit terrible acts of exploitation on children.

"We lash out and blame social workers because it is easy but we should all feel a sense of guilt when things go wrong. It is all our duties to protect children in the adoption system."