A teenager who murdered a man in a "cowardly and senseless" knife attack has been ordered to be detained for at least 14 years.

Haris Mohammed, 16, remained unemotional in the dock at Nottingham Crown Court as he was sentenced for killing refuse worker Tom Webb.

Mr Webb died in hospital after being stabbed in the chest by Mohammed in Derby city centre on January 19 while on a night out with friends.

The 22-year-old victim was attacked by Mohammed, who had taken a butterfly knife with him into the city, after a "chance remark" about a passing young woman sparked a confrontation.

Ordering Mohammed to be detained at Her Majesty's pleasure - the juvenile equivalent of a life sentence, Mrs Justice Cox told him: "The victim personal statements (from Mr Webb's mother and his fiancee) describe in poignant and moving detail the extent of their grief.

"The fact that you were carrying in a public place, and at night, the knife which you then used in the fatal attack is without doubt a serious aggravating feature in this case.

"You could so easily have turned and walked away."

Mohammed, of Allenton, Derby, was convicted of murder by a jury a fortnight ago after four hours of deliberations.

During her sentencing remarks, Mrs Justice Cox told the teenage killer: "It is clear that you continue to assert that which you told the jury - that you were trying to defend yourself.

"You most certainly were not. Tom Webb was out in the town with his two best friends. They were not looking for trouble and had caused no trouble for anyone at any stage.

"They posed no threat to you whatsoever. I reject entirely the suggestion that you felt yourself to be under threat from Tom."

Before sentence was handed down, the victim's mother, Rachel Webb, spoke at length in the witness box about her only child, who planned to join the Navy.

After thanking the judge for the opportunity to address the court, Ms Webb, who suffers from post-traumatic stress, said: "Tom was a warm, kind, thoughtful and loved son, who had just started out on his life journey.

"Tom will never have a future and the pain this causes me is indescribable."

The court heard Mohammed took six GCSEs and other courses while on remand.

Offering mitigation for the teenager, defence barrister Peter Joyce QC told the court: "He has started to understand the depth of the harm that he has done and to seek to improve himself."

Reporting restrictions banning the identification of Mohammed were lifted at an earlier hearing.

In a statement issued after the case, Karen Thompson, deputy chief crown prosecutor for CPS East Midlands said: "Tom Webb's murder was a completely senseless and tragic waste of a young life.

"There was no need for Haris Mohammed to be carrying a knife, there was no need for any kind of confrontation, and there was certainly no need to use the knife on Mr Webb.

"These were all choices made by Haris Mohammed.

"My heartfelt sympathies are with Tom's family and friends. They have had to endure a terrible loss and I hope that the conclusion of this case will enable them to start to rebuild their lives."

Detective Chief Inspector Dave Cox, who led the investigation, said: "I hope that this sentence sends a strong message to anyone who is thinking of carrying a knife.

"A young man lost his life that night and another youngster will now be spending at least 14 years behind bars."