The family of a teenage girl who was fatally stabbed during a fight with her boyfriend broke down as he was sentenced to little over two years in prison.

Police said Katrina Makunova, 17, died after falling on a knife inside her own handbag, but her family said 21-year-old Oluwaseyi Dada had been repeatedly reported for previous physical attacks.

The Independent Office for Police Conduct (IOPC) is investigating how police responded to five allegations of assault and harassment made by Ms Makunova in the months before her death.

Dada pleaded guilty to manslaughter on the first day of his trial at Southwark Crown Court and was jailed for two years and three months on Thursday.

On that Dada would serve half of the sentence before being released on licence, Ms Makunova’s relatives broke down in tears and one family member shouted: “Are you serious? It's a f***ing joke. She was 17 years (old). One year for my sister.”

They left court followed by police liaison officers, and further shouting could be heard from outside the courtroom.

Judge Nicholas Loraine-Smith called the case “extraordinary” and told the court Ms Makunova died from a single knife wound at a block of flats in south London.

“The kitchen knife that caused her death was hers and had, it seems, been brought to the scene by her in a handbag you had given her,” he told Dada.

"It appears that somehow in the struggle between you and her, the blade of the knife was pushed through the bag from the inside and tragically pierced her chest and heart.

“There is no evidence that you ever touched it before she received her fatal injury.”

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The court heard that the pair exchanged heated and threatening texts after their two-year relationship deteriorated, including messages declaring “let the party begin”, “I actually dare you to come in”, “so are you bringing people yes or no”, and “am gonna burn your mum right now”.

The judge told Dada: “These messages must be seen in context of other messages sent by you a few days earlier that read 'don't piss me off', 'is cause no-ones been touched u think I am a joke' and 'don't play that game before I stab you'.”

The judge said Dada had helped to build up “the tension” ahead of the confrontation at the block of flats where he lived in on Brisbane Street, Camberwell, on 12 July.

Judge Loraine-Smith said Ms Makunova “expected it to be so serious" that she arrived with a knife in her handbag.

"Doubtless you expected that she would be armed and so you did confront her, you grabbed her handbag,” he told Dada.

"In the course of the struggle you took hold of her, pushed her and she fell.”

The judge added that the confrontation “could so easily have been avoided” if Dada had stayed in his flat or left the building.

He was initially arrested on suspicion of murder but subsequently charged with manslaughter as the investigation progressed.

In the months before Ms Makunova’s death, she made several allegations of assault and harassment against Dada to police.

Oluwaseyi Dada, 21, admitted manslaughter (Metropolitan Police)

Officers had become involved “no less than six times” in the last months of the couple's relationship, the court heard.

The last reported incident was on 26 June, when Dada threw a drink over Ms Makunova. It was still being investigated by police when she died.

Detective Inspector Domenica Catino, of the Metropolitan Police Homicide and Major Crime Command, said: “A young woman has lost her life and our thoughts remain with her family and friends, who have been devastated by Katrina's death. This case is a tragedy for everyone involved.”

Det Insp Catino said Ms Makunova’s knife was “never taken out of the bag” before piercing her chest and added: “This is unfortunately another sad example of the consequences of carrying knives. We must all work hard to prevent any further loss of lives.”

The IOPC said was investigating Metropolitan Police officers who were in contact with Ms Makunova from February to June last year.

"The contact included the police’s response to five allegations of assault and harassment made by Ms Makunova against Dada," a statement said.

"Five Metropolitan Police officers involved in the investigation and supervision of these allegations have been notified their conduct is under investigation."

The probe has been underway since July 2018 but was not announced, for legal reasons, until Dada admitted manslaughter.

Ms Makunova was among 24 victims aged 19 or under who were killed in London in 2018.

The total of 134 homicides recorded in the year was the capital’s highest total since 2008, which saw 154 people killed, and a 15 per cent rise year-on-year.