A grieving widow spoke of her "shock" after Jeremy Corbyn failed to respond to her plea for an inquiry into the death of her husband at the hands of a mentally-ill foreign student.
Proud new father and renowned academic Dr Jeroen Ensink, 41, was stabbed to death by Femi Nandap on his doorstep in Islington, north London, on December 29 last year.
Police had earlier been alerted that Nandap, 23, was receiving treatment in his native Nigeria despite being on conditional bail in the UK awaiting trial on knife charges.
Then just days before the killing, the Crown Prosecution Service dropped the case against him, the Old Bailey heard.
Prosecutors admitted a mistake, but Dr Ensink's widow still has unanswered questions and says lessons have not been learned from the tragedy as it is "swept under the carpet".
Nadja Ensink-Teich had called for an inquiry into what went wrong as Nandap was handed an indefinite hospital order in October.
Since then, she has emailed politicians for help, including Islington MP and Labour leader Mr Corbyn and Mayor of London Sadiq Khan. Not one responded.
Speaking to the Press Association ahead of the anniversary of her husband's death, she said: "It's almost like it never happened. It's hard to say where we go from here.
"It's just so complex, after what I called the media marathon, there was hardly anything. There was a lot of interest from the public and everybody was very shocked.
"But what it boils down to, even though I have sent emails to MPs, Home Office and the mayor of London, they have not even replied.
"I have not even had a reply back, not even a 'so sorry for your loss', absolutely nothing. I just find that shocking and unbelievable and makes me think what are they actually doing? Why are they in their job?
"It was just an open email asking for an independent investigation and it's completely brushed under the carpet - if you don't talk about it, the problem doesn't exist."
She went on: "It's just frustrating. Lessons clearly have not been learned and quite honestly, I don't think they want to learn the lessons. It's an issue of austerity, it's an issue of not sharing information.
"The CPS did not even know that he was in a mental hospital. If they had known about that before, he would have got psychiatric help and then it might not have happened.
"There are so many points I want to address but I think the main issue is it doesn't get attention it needs. It's not taken seriously enough. It's almost like there's not a problem if you don't talk about it."
A spokeswoman for Mr Corbyn said: "Jeremy takes his responsibilities as a constituency MP extremely seriously and is regarded as a diligent and committed local MP.
"He apologises for any failure to respond to an email and invites Nadja Ensink-Teich to contact his constituency office to arrange an appointment."
The Deputy Mayor for policing, Sophie Linden, said: "This was a brutal and tragic attack, and our thoughts are with Nadja and her family at this very difficult time."
It is understood that the Mayor's office found no record of any correspondence but were now getting in touch directly.
Nandap had admitted manslaughter by diminished responsibility and was sentenced in October.
He told psychiatrists that he started to receive telepathic messages and considered himself the ''chosen one'' or ''Messiah'' in spring 2015.
While on conditional bail for knife-related charges, he went to Nigeria where he was treated with anti-psychotic drugs, which he stopped taking by his return to the UK.
On August 25, his sister had handed a letter to police explaining he was not fit to travel back to the UK earlier because he was suffering ''depression and psychosis''.
Just six days before he attacked Dr Ensink, Nandap had charges of possession of a knife and assaulting a police officer dropped at magistrates' court.
Dr Ensink was repeatedly stabbed as he left his flat to post cards announcing the birth of his daughter Fleur.
When he failed to return home, his wife went outside and saw the blood-stained cards strewn on the pavement.
During the course of 2016, Old Bailey judges have dealt with 10 serious cases in which the defendants were known to have mental health problems before attacking people.
In all, 10 defendants left 10 people dead and another two members of the public seriously injured.
Julian Hendy, of Hundred Families charity, has supported Mrs Ensink-Teich and a host of other families.
He said: "There are around one hundred killings by people with serious mental illness in the UK each year and our research shows that the numbers are increasing.
"We know mental health services are currently under severe pressure in this country, but we also know that they are often failing to learn and prevent these tragedies. Often they don't assess the risk properly, plan the care effectively or listen well enough to the families involved.
"And if they don't learn, these avoidable killings will continue.
"They are not single victims - each of them had a family, friends and lived in communities that have all been deeply and profoundly affected by their deaths.
"We continue to support as many of the families in these cases as possible, and work with the NHS so that no other family will have to experience the pain, trauma and loss that our families continue to endure."
Mrs Ensink-Teich has since left her Islington home in the street where her husband was killed and moved back to Holland with her young daughter.