Valdo Calocane, 32, was suffering from paranoid schizophrenia when he stabbed students Barnaby Webber and Grace O'Malley-Kumar, both 19, and school caretaker Ian Coates, 65, in Nottingham in the early hours of 13 June 2023.

He has admitted three counts of manslaughter, by reason of diminished responsibility, and three of attempted murder after hitting three other pedestrians with a van he stole from Mr Coates. He will be sentenced this week.

Although Calocane had no previous convictions, Nottingham Crown Court was told that he had been arrested for assaulting a police officer, involved in incidents of criminal damage and once visited MI5's London headquarters to ask them to stop "controlling him".

Around seven months worth of unused medication was also found at his property in 2021, with prosecutor Karim Khalil KC telling the court on Tuesday that there was a "constantly recurring" theme that Calocane was prescribed medication but declined to take it.

Rob Griffin, Nottinghamshire Police's assistant chief constable, admitted in a statement released on Wednesday that more could have been done to arrest Calocane at the time of the alleged assault on an officer in September 2021.

"I have personally reviewed this matter and we should have done more to arrest him," he said.

But it is "highly unlikely" Calocane would have received a custodial sentence for the assault, Mr Griffin added.

"Of course, an arrest might have triggered a route back into mental health services but, as we have seen from his previous encounters with those services, it seems unlikely that he would have engaged in this process."

Here is a timeline of all the occasions Calocane was involved with mental health services or police, right up to the month of the "atrocious" killings.

23 May 2020

Calocane went to hospital believing he was having a heart attack. He was later arrested after causing damage to a door on returning to his flat.

An assessment by psychiatric services under the Mental Health Act 1983 was carried out at a Nottingham custody suite, where it was concluded that Calocane was psychotic but that his risk to others was low.

He was released without charge and referred to a crisis team for review at home.

An hour after he returned to his flat, Calocane "knocked down another door to a different apartment in the block".

He was arrested for criminal damage and after a re-assessment was detained under the Mental Health Act and admitted to in-patient psychiatric services at the Highbury Hospital in Nottingham.

He was diagnosed as a paranoid schizophrenic, according to defence barrister Peter Joyce KC.

July 2020

After his release from Highbury Hospital in June 2020, the court heard he was readmitted for a period during July 2020, after attempting to force his way into a flat, after having stopped taking his medication.

August 2021

Prosecutor Mr Khalil told the court that Calocane was believed to have actively concealed symptoms of psychosis during a home visit by a mental health worker.

He then evaded contact with the community team.

Officers obtained a warrant under the Mental Health Act to gain entry to Calocane's property so that an assessment could be conducted.

3 September 2021

Officers executed the warrant. It was during this search that Calocane allegedly assaulted a police officer.

"A bag of unused medication dating from February 2021 was also discovered in the flat," prosecutor Mr Khalil said.

"He was admitted to in-patient services and managed between September and October 2021."

"Thereafter he had limited contact with his community team, appearing confrontational and missing appointments," Mr Khalil told the court.

January/February 2022

Calocane was involved in an altercation with a flatmate.

A subsequent mental health assessment concluded that he could continue to be treated in the community.

At the end of January, Calocane was again admitted as an inpatient under the Mental Health Act, and discharged on 24 February.

Approximately six months before the attacks, Calocane was living in a multi-occupancy house in Burford Road, Nottingham, where a housemate found him to be "somewhat distant, never speaking unless spoken to and only then giving short responses".

March/July 2022

Calocane was reviewed at an outpatient clinic, and in July 2022 he is believed to have falsely claimed that he was not in the country.

August/September 2022

Calocane was recorded as not being at home following a visit to his discharge address, with a resident saying no one of that name lived there.

A warrant for his arrest for assaulting a police officer was issued again after he failed to attend court in September.

May 2023

Five weeks before he killed three people, Calocane started working in a warehouse in Kegworth, Leicestershire, where he attacked two employees.

Efforts were made to tell him he was not allowed back on the premises, but Calocane did not respond.

June 2023

Calocane had been wanted on a warrant in Nottingham for nine months, for the assault on a police officer that happened back in September 2021, according to defence barrister Mr Joyce.

But he was free to carry out the attacks on 13 June last year.

Assistant Chief Constable Griffin added: "The defendant was never arrested for that warrant which was still outstanding at the point of his arrest in June 2023."