Femi Nandap (left), 23, was suffering from cannabis-induced psychosis when he murdered academic Dr Jeroen Ensink, 41,  as he left his flat in Islington, north London

A crazed Nigerian killer who stabbed a father to death on his doorstep will be kicked out of the UK once he is fit for release.

British taxpayers will continue to foot the bill of Femi Nandap's incarceration and mental health treatment during his sentence at Broadmoor secure hospital in Berkshire, until he is deemed safe to be in the public, a judge has revealed.

Student Nandap, 23, was suffering from cannabis-induced psychosis when he murdered academic Dr Jeroen Ensink, 41, as he left his flat in Islington, north London, in December last year.

Dr Ensink, a renowned water engineer and a dedicated humanitarian, had gone out to post cards announcing the birth of his 10-day-old daughter Fleur on the day of the attack.

Earlier this year, Nandap admitted manslaughter by diminished responsibility and was handed a hospital order with no time limit by an Old Bailey judge.

Judge Nicholas Hilliard, QC, has now held a further hearing to discuss whether to make a further deportation order in the event the killer is ever safe to release from Broadmoor.

He outlined the issues and said the Home Office had confirmed that Nandap's continued leave to remain in Britain had been 'cancelled' and now he has 'not got any right to remain in the UK'.

He said: 'In these circumstances, if the time came, if he were close to being released, Broadmoor hospital would inform the Home Office immigration enforcement section and they would consider whether he should be deported.

'In those circumstances, the Crown are not asking me to make an order. I can see the reason why and I am not proposing to make one. It seems to me it would be covered in other ways.'

Dr Ensink was killed just yards from his front door shortly after Christmas last year

Earlier, the court had heard how Nandap came to Britain to study African studies and economic development on a student visa.

In Spring last year, he became psychotic from smoking cannabis and believed voices telling him he was a 'Messiah'.

In May 2015, he was arrested for wielding a knife in public and punching and biting a police officer. While on conditional bail, Nandap went home to Nigeria where he was treated for mental illness.

His sister informed British police about his condition in August and handed in a certificate saying he was unfit to travel.

Dr Ensink's wife holds the couple's daughter Fleur - who was 10 days old when her father died

On his return in October, Nandap had stopped taking anti-psychotic drugs. Then just six days before the killing, charges against him were dropped at magistrates court in December.

The prosecution admitted the decision to drop charges against Nandap of having a knife and assaulting a police officer was wrong.

Dr Ensink's widow Nadja has demanded an inquiry into how Nandap was free to carry out the killing.

She said in October: 'If a person with a history of mental health problems is found wandering about with a knife, and attacks a police officer, then that person must be referred to a secure unit for proper assessment and treatment and not given bail so easily.

Dr Ensink's widow Nadja has demanded an inquiry into how Nandap was free to carry out the brutal killing

'This represents a failure of the health and judicial system that should protect the public and care for those with severe mental illness.'

Dr Ensink, originally from Holland, worked at the London School of Hygiene and Tropical Medicine.

He was committed to improving access to water and sanitation in deprived countries.