A 16-year-old boy has today been jailed for at least 12 years after murdering a fellow teenager on a busy bus.

Shawn Green, who was 15 at the time, boarded a packed 393 bus in Highbury, pushed past horrified passengers – including a woman with a baby in a papoose – and stabbed Derek Boateng in the heart with a kitchen knife before jumping off.

Derek, of Graham Road, Hackney, who was celebrating his 16th birthday, remained standing for a minute or so before collapsing “as though he had been hit by a train” on the street in Highbury New Park, outside Highbury Grove School, where Green was a pupil.

Derek, a former Highbury Grove pupil, was airlifted to hospital but died the following day, on April 24, after suffering massive internal bleeding.

Passing a sentence of detention during Her Majesty’s Pleasure with a minimum of 12 years, Judge Peter Thornton QC said: “You were just 15-years-old and a school boy in uniform when you stabbed to death another boy on his 16th birthday.”

He added: “I have seen no remorse, no expression of regret on your part for the loss of Derek’s life.”

In an impact statement Derek’s parents Davis and Comfort, who were present throughout the trial, said: “The death of Derek has left our whole family devastated. Our whole world has collapsed right in front of us.

“We never thought in a million years this tragedy would come to our doorstep. Everything has changed completely.

“The thought of not seeing him again is heart-breaking. Sometimes we think we will see him again, but we know we cannot.”

Judge Thornton described how Green, of Nightingale Crescent, Romford, boarded the bus, saw Derek, looked around to make sure he was alone and made a beeline for him.

The motive for the attack, he said, was unclear – although Green had told the court he was angry after being attacked by Derek and some other boys six months earlier.

“Whatever the reason,” said the judge “you attacked him and killed him. Sadly he had a knife and produced it to defend himself.

“You leant over woman in the aisle seat and stabbed him in the chest.

“A knife is a weapon that cuts and kills so easily.”

He added: “You were seen watching Derek as he collapsed on the bus. You knew then at least you had injured him severely.

“That’s why you went to the flats to dispose of knife.”

Green noticed a man watching him and moved on. The murder weapon was never recovered.

The killer claimed he carried the knife because he was scared after an alleged attack by Derek six months ago, an explanation which Judge Thornton said “did not ring true” and offered no mitigation.

He said the jury had rejected his claims of self defence and that the “courts would do everything they can to stop this terrible crime.”