A youth, who launched a screwdriver attack on an 18-year-old who asked why he was staring at him was sentenced to 30 months' detention on Friday.

The 17-year-old - who cannot be named for legal reasons - repeatedly stabbed Anthony Knowles outside the station in Cassiobury Park in Watford.

Prosecutor Isabel Delamare said the youth, who comes from Wembley, and a friend were on the train at 1.30pm in August, when he began to stare at Mr Knowles.

When it reached Watford all three got off and Mr Knowles asked: "Is there a problem?" The defendant said: "Come outside" and Mr Knowles replied: "Shut up."

A friend picked Mr Knowles up outside the station, but Ms Delamere said that the youth waved the car down, lent inside the open passenger window and repeatedly stabbed Mr Knowles with the screwdriver, saying he was going to kill him.

The driver sped off and took the victim straight to Watford General Hospital, where he received stitches to wounds to his upper arm and back. A doctor said the wound came close to puncturing a lung.

The police arrested the teenager in Wembley two days later. He pleaded guilty to wounding Mr Knowles with intent and appeared for sentence via a video link from Feltham young offenders' prison.

He had previous convictions going back to the age of 13. Since being held in Feltham he had knocked out a fellow inmate, caused two prison officers to be taken to hospital and had been found with an offensive weapon in his cell.

Sitting at St Albans Crown Court, Judge Andrew Bright QC said: "I take the view he is dangerous and I hope that those responsible for his licence when he is released are aware of it. He needs a lot of support and help."

Sentencing the youth, he said he had been found to be "emotionally detached" from what he does and was at a high risk of re-offending. He told him: "When you lose your temper you are almost beyond control and that needs to be addressed by those who have care of you."