She lost the impartiality and objectivity to be expected of a prison officer.

Mr Justice Owen

Mrs Armstrong, of West Down, Ferndown, Dorset, had, along with several other officers, supervised West in Holloway.

She then transferred with her to Winchester, where Rosemary West stood trial in 1995.

Mrs Armstrong took it upon herself to befriend West to try and reduce the risk of her committing suicide.

This, it was claimed, made her vulnerable as she had been building up a relationship with West over a considerable amount of time.

'Life goes on'

The judge said Mrs Armstrong departed from the high standard of professional detachment that she normally set herself and allowed herself to become emotionally involved with West.

He said: "As her counsel put it in opening, she lost the impartiality and objectivity to be expected of a prison officer.

"But that was not the result of any acts of omissions on the part of the defendants."

A costs order was made in favour of the Home Office, which had denied liability.

After the judgment Mrs Armstrong said: "This is not a tragedy. What happened in New York was a tragedy. Life goes on."

Mrs Armstrong, who is now retired and legally aided, was refused leave to appeal but can apply to the Court of Appeal direct.