One of the youngest murderers in the UK has been sentenced to 11 years behind bars for stabbing a 53-year-old man to death.

The 13-year-old, who cannot be named for legal reasons, stabbed Christopher John Barry, known as Jack, in the chest on December 14, following an argument outside a block of flats in The Broadway, Edmonton.

The boy, who was part of the Wood Green gang, had been trying to get back into a party but had gone to the wrong block of flats.

A fight broke out between the 13-year-old and Mr Barry as he refused to let him into the block.

He then produced a kitchen knife from his back shouting “What you saying now? What you saying now?”

The teenager managed to get into the block of flats, where he stabbed Mr Barry as he got into the lift.

He was arrested at his school two days later.

At the Old Bailey today, prosecutor Zoe Johnson urged Judge Stephen Kramer to give the minimum sentence of 12 years for a boy of his age for murder.

She also told the court of a previous warning the boy had been given for possession of a knife at school and for possession of cannabis.

In a statement, Mr Barry’s girlfriend, Sabrina Finn, said her heart was “broken” and described how Mr Barry he had saved her life in the past.

It reads: "Jack's murder had a huge emotional impact on my life. I am now very anxious when going out, particularly when I see groups of young people wearing hoodies in the street. I feel very vulnerable. I also feel anxious about possibly seeing the boy who murdered Jack and bumping into him one day.

"I am not sleeping well and wake up in the night remembering the awful way Jack died, realising that I'm on my own again and feeling very frightened and lonely.

"I am back at work now and although I walk, talk and look the same as before, inside I am tired and my heart is broken. Jack and I had four happy years together and this young boy has taken that happiness away from me. For that I am very sad and angry as my life will never be the same again.

"Jack saved my life last year when I had a serious medical condition which required emergency surgery. Unfortunately I could not do the same for him. Rest in peace Jack."

In his summing up statement, Judge Kramer said: “You are 13. But you were carrying a knife in your bag and wanted to get into a block of flats to get back to some friends.

“But you went to the wrong block with tragic consequences for everybody.

“Christopher Barry had been out walking with his girlfriend and refused to let you in to where he lived. You followed him, produced your knife and stabbed him twice in the chest.

“You took a knife to the scene, you put it in your back pack and deliberately took it out and stabbed him with it.”