The woman who triggered the investigation into serial killer Harold Shipman has told a public inquiry she thought she was mad to be suspicious about the former GP.

Angela Woodruff, whose mother Kathleen Grundy was Shipman's 215th and last victim, said she felt she was "in almost an Alice In Wonderland world" because her fears seemed so unbelievable.

As the inquiry's final phase opened on Monday, the hearing was also told NHS systems provided no safeguard to stop the killings.

The inquiry is likely to continue into next year and will examine how Shipman got away with the murders for so long.

Kathleen Grundy was Shipman's last victim

Mrs Woodruff, a lawyer, told the hearing in Manchester about how her and her husband felt as their suspicions grew.

"We kept thinking it looked as though Dr Shipman had done something but it couldn't be and we couldn't believe it," said Mrs Woodruff.

"We were thinking we were going mad. We even had various theories, such as that my mum was really ill and had asked the doctor to help her die or that she had committed suicide.

"But I couldn't imagine anyone more unlikely to do that. It was an unreal world we were living in."

It was only when she got another lawyer to assess the evidence that Mrs Woodruff became convinced she was right.

She added she believed that a second doctor should be required to inspect the body, examine medical records and speak to relatives in all deaths.

She said: "I think it is very, very important to speak to relatives.

"I realise that in so many cases, had the relatives known the facts about their loved one's death, things would have been very different."

Angela Woodruff said she thought she was going mad

Caroline Swift QC, counsel to the inquiry, had earlier said Shipman, manipulated systems in order to commit murder without detection.

Ms Swift said that when Shipman's crimes came to light it was down to the clumsy way he forged Mrs Grundy's will and not because of any "warning bell" activated by the system.

"It is therefore clear the existing systems provided no safeguard at all against a determined killer within the medical profession," she said.

She said of Mrs Grundy's death: "It was [one] which any honest doctor would have to refer to the coroner.

"But Shipman was not an honest doctor and in order to conceal the fact he murdered Mrs Grundy, it was imperative to avoid a formal report to the coroner."

Issues to be addressed in the inquiry include the issuing of death certificates, the reporting of sudden deaths and access to controlled drugs.

A report from the first phase, published in July, concluded that the Hyde GP had killed 171 women and 44 men.

Shipman was originally convicted in January 2000 of killing 15 of his patients with lethal heroin injections and was sentenced to life imprisonment for each of the murders.