A 17-year-old boy has been locked up for six-and-a-half years for killing a woman “in a fit of anger” during a laughing gas-fuelled row last Christmas Eve.

The youth, who cannot be identified, had argued with 22-year-old mother Kacey Clarke and stabbed her in the chest in a flat in Bermondsey, south-east London.

The defendant was cleared of murder after a trial but convicted of manslaughter and was sentenced at the Old Bailey on Friday.

The court was told that at the time of the killing, he was on bail for a series of e-bike mobile phone snatches, having stolen 34 devices valued at £28,000.

Sentencing, Judge Simon Mayo KC told the defendant: “I am sure that in a fit of anger you picked up a hunting knife… removed it from the sheath and stabbed her in the side of the chest.

“I accept you did not plan to stab her and that your decision to do so was formed in the moments before you did so.

“I also accept you regret what you did and the remorse you have expressed is genuine. You will forever have to live with the fact that in that moment of anger you stole Kacey’s life.”

The judge noted a statement from Ms Clarke’s uncle Steve Armstrong who described the “huge impact” her death has had, leaving an “immense hole in our hearts and in our lives”.

The judge said he was satisfied both the defendant and Ms Clarke were “under the influence” of nitrous oxide at the time of the killing.

He imposed no separate sentence for a charge of conspiracy to rob relating to the mobile phone snatches and six counts of dangerous driving.

The court was told the youth rode an e-bike on the pavement, narrowly avoiding pedestrians.

Previously, the court heard how a row began over Ms Clarke’s missing car keys, which she had mislaid.

The youth was caught on CCTV threatening to “ching” up and kill her.

The court was told Ms Clarke had thrown an object at the youth and pulled a clump of his hair out.

But the judge rejected the defendant’s claim she had a knife before he armed himself with a hunting knife in self-defence.

Police and paramedics were called just after 10pm and found Ms Clarke lying on the kitchen floor of the flat with a single stab wound to the chest.

The defendant was arrested nearby around 45 minutes later.

The hunting knife was hidden in a railway arch, where it was discovered by a Thames Water workman on January 17.

Like the victim, the boy was said to have a history of inhaling nitrous oxide – commonly known as laughing gas – which was classified a class C drug in November 2023 in a crackdown on anti-social behaviour.

A search of the youth’s bedroom revealed a large collection of canisters, the jury was told.

The court heard the defendant had a history of possessing knives, having been caught with a 25cm long Rambo-style blade in an ice cream shop and a lock knife in his waistband in a residential area.

In all, he had convictions for 25 offences between April 2022 and September 2023.

In mitigation, it was asserted that although the youth had carried knives there was a lack of threatening behaviour and that Ms Clarke “had her demons”.