On the street: The WPC killer so dangerous even police officers are warned not to approach him

Magdi Elgizouli, 40, who has a deluded hatred of the police, has been granted leave from a secure psychiatric unit four hours a week in preparation for his permanent release.

He is also allowed out a further five hours each month to visit his brother.

Dangerous: Left, WPC Mackay in uniform, and her killer Magdi Elgizouli

Mental health chiefs say they believe Elgizouli's psychiatric condition has improved significantly since he killed WPC Nina Mackay, and have granted him supervised release to help reintegrate him back into society.

However, police disagree, and an urgent message has been issued under Scotland Yard's 'officer alert system' warning that Elgizouli is a grave threat to officers' safety and should not be approached.

WPC Mackay's father - retired Metropolitan Police Chief Superintendent Sidney Mackay - has also reacted angrily after belatedly learning that Elgizouli has been given leave from St Bernard's Hospital in Southall, West London.

Jobless drifter Elgizouli stabbed his daughter to death with a seven-and-a-half-inch kitchen knife as the 25-year-old went to arrest him at a flat in Stratford, East London in October 1997.

Moments before her death, WPC Mackay removed the body armour that could have saved her life because the protective vest was hampering her movement.

At the time, Elgizouli was in breach of bail conditions for assaulting a police officer and possessing an offensive weapon, a knife, 11 days earlier.

Victim: Nina Mackay was knifed to death in October 1997

In April 1998, he was detained indefinitely and ordered to be sent to Rampton maximum security hospital in Nottinghamshire after admitting manslaughter on the grounds of diminished responsibility.

The Old Bailey heard he had been 'very ill' at the time of the killing because he had refused to take the necessary medication for his illness.

Since being locked up, Elgizouli - who was born in Britain but is of Sudanese origin - is said to have responded well to treatment. He is now a patient at a secure unit in St Bernard's as preparations are made for his eventual release.

In a letter to the Mental Health Review Tribunal, WPC Mackay's father said: 'Can I remind you that the death of our daughter remains as painful today as when it happened over ten years ago?

The opportunity for her to visit us for five hours per month would be overwhelming. That is not going to happen and our sentence continues unabated.

'I am well aware the changes to Elgizouli's condition are preparatory to his ultimate release into the community and I will do my best to ensure that those responsible are subsequently held accountable if he disappears or some dreadful happening occurs.

'A little more openness about your intentions, unpalatable as we may find them, would be much appreciated in the future.

We remain the living victims of this dreadful event and owe it to the memory and love we bear our daughter not to see her death disappear as another statistic for an academic to ponder over, while the person responsible resumes his life as if nothing happened.'

Mr Mackay told the Daily Mail: 'This is a man who became psychotic-through the use of cannabis and has expressed hatred for the police.

'In the run-up to the death of my daughter, he refused to take his medication and jumped bail. I cannot believe he has changed much in the intervening years.'

An MHRT official said the patient's 'overall care rests with the detaining hospital'.

In a letter sent to Mr Mackay earlier this month, the Ministry of Justice said that, for confidentiality reasons, it could not confirm any details about Elgizouli.

An official added: 'It is not the case that leave indicates discharge is imminent.'

Mr Mackay's grief was compounded five years ago when the Home Office ruled his daughter would not be honoured for her courage by receiving the Queen' s Gallantry Medal.