A 15 year-old public schoolboy who stabbed his best friend in the chest during a ‘bad trip’ on LSD at his parent’s £1.8million home was spared jail today.

The gifted teenager, who cannot be named, plunged a seven-inch kitchen knife into the chest of the victim - missing the heart by less than half an inch - because he believed the boy was the Devil.

By chance the blade did not cause lasting injuries despite puncturing the lung and his friend, also 15, has made a full recovery after spending only one day in hospital.

The schoolboy had ‘gone off the rails’ despite his privileged background and had been taking a cocktail of cannabis, cocaine and ketamine in the year leading up to the attack, the Old Bailey heard.

The schoolboy had ‘gone off the rails’ despite his privileged background and had been taking cannabis, cocaine and ketamine in the year leading up to the attack, the Old Bailey heard

He was originally charged with attempted murder but the prosecution accepted a plea to the lesser charge of unlawful wounding on the grounds he did not realise what he was doing at the time.

Judge Richard Marks QC told the boy: ‘This case is a vivid reminder and demonstration if ever one were needed of how extremely dangerous drugs can be for the simple reason that you have no idea what you are taking nor how the drugs may affect you.’

The teenager sat in the witness box as he was sentenced to a 12 month youth rehabilitation order with three months on an electronically tagged curfew between 8pm and 7am.

Judge Marks said: ‘I want to make it clear to you that the background you have come from is not a mitigating factor but rather an aggravating feature in your case.

‘With all the advantages you have had in life you should have had more sense and self control than getting involved in class A drugs and understanding where that might lead.

‘That said I do regard this as a wholly exceptional case and I am prepared to deal with you by imposing a youth rehabilitation order.

‘You owe a great deal of gratitude to many people who have come together to assist you, not least your parents for whom this must have been a terrible ordeal.’

The boy, who cannot be identified because of his age, was a pupil in year 10 at a public and lived with his parents and sister in a leafy suburb in south London.

Neither his mother nor his father knew he had been taking drugs for the past year although there were tensions at home and his schoolwork had deteriorated, the court heard.

Judge Richard Marks QC (pictured) told the boy the case was 'a vivid reminder and demonstration how extremely dangerous drugs can be'

On 16 December last year, a few days after school broke up for the Christmas holidays, he spent the day with his friend by visiting an art gallery in Sloane Square.

The pair then travelled to Ravenscourt Park to buy drugs from their regular dealer, met some friends and then returned to the schoolboy’s home for the night at around midnight.

While his sister and parents were in bed, the boys watched a movie before taking the LSD.

His friend later told police the boy ‘reacted badly to the acid’ and was ‘looking around as if in another world’.

The boy appeared confused, began talking to himself and asked “How can I kill myself” before trying to leave the house.

His friend took the boy back to the kitchen before being suddenly pushed to the floor and stabbed.

Prosecutor Anita Arora said: ‘He took a kitchen knife and plunged it into his friend’s chest with full force.

‘The blade penetrated one centimetre from his heart and his lung could be seen clearly through the open wound.

‘His friend later told police it was all surreal and he could not feel his wound and did not believe he had been stabbed.’

The friend also described the boy as ‘out of it’ and claimed that they had not argued and the stabbing was not done maliciously.

At around 3.30am the boy’s father was woken by the sound of a bang followed by shouting and went downstairs to find the victim wrapped in a bloodstained sheet.

They called the emergency services and roused a surgeon living nearby to try and help.

The victim told the surgeon that they had both taken acid and that the boy ‘had a bad trip’.

Police officers who attended the scene described the attacker as gurning his lips and appearing not to understand what was happening.

The boy was heard to ask: ‘When will this end’ and ‘When do memories start.’

He did not answer questions in police interview but gave a statement admitting he had taken acid.

‘At first I was find but then I started getting scared. I remember picking up a knife. I do not remember stabbing [my friend]. I remember my parents coming and seeing him covered in blood.

‘Although I can’t remember stabbing him I accept I must have done. I feel really awful about the whole thing. He is my best friend, I would never want to hurt him.’

Tests on a blood sample taken at 4pm on 18 December revealed only the presence of cocaine as the LSD may have been eliminated from the system since over the 12 hours since the attack.

The victim had suffered a single knife wound which had caused a collapsed left lung, bleeding in the chest cavity and a fracture to the third rib and was discharged from hospital the following day.

Crispin Aylett, QC, representing the attacker, said the youth had spent four weeks locked up at a secure training facility after the stabbing and had been wearing an electronic tag since.

The boy was originally charged with attempted murder but the prosecution accepted a plea to the lesser charge of unlawful wounding on the grounds he did not realise what he was doing at the time. Pictured: The Old Bailey in London

‘Instead of spending Christmas with his family and friends he found himself locked up and far from home. If he has not learnt from that then he wouldn’t learn from anything.

‘Nobody underestimates the seriousness of this incident which could have had catastrophic consequences,’ said Mr Aylett.

‘It could have been very much worse and it is fortunate that the victim appears to have made a complete recovery, albeit that is perhaps a matter of chance.’

Mr Aylett said the boy ‘had been going off the rails for some time’ and said: ‘He had been experimenting with drugs and there had been tensions with his parents. There was undoubtedly a lack of interest and effort at school.’

The court heard the boy has been receiving tutoring at home since the attack and will attend a college over the summer before possibly returning to school for Year 11 and his GCSEs.

Judge Marks said: ‘It appears that you were having what is sometimes called a bad trip almost certainly as a result of the effects of the LSD.

‘You were clearly confused and appeared to be in a world of your own.

‘Evidently believing at the time that your friend was the devil you pinned him down on the floor, sat astride his chest and stabbed him once in the chest with full force.

‘By dint of good fortune the knife missed his heart by one centimetre.

‘You could have easily found yourself in this court facing a murder charge for which had you been convicted there would have been a sentence of life imprisonment.

‘It is apparent that you are gifted both academically and in sport and in your previous year had been doing extremely well.

‘In Year 10 you started to go rapidly downhill. Your relationship with your parents deteriorated badly and there can be no doubt that all of this must be in large measure down to the fact that you have been involved in regular taking of drugs.’

The judge said the guidelines for sentencing young people suggested that prison should only be used a ‘last resort’.

‘If you had been an adult an immediate custodial sentence would have been inevitable,' he said.

‘I accept your behaviour that night was out of character and it is most unlikely you will re-offend.’

The 15 year-old boy, from south London, hugged his mother and smiled before walking out of court.

He pleaded guilty to unlawful wounding at an earlier hearing.