A UNIVERSITY dropout who stabbed his mum to death as she slept after smoking 'huge' quantities of cannabis has today been given a life sentence.

Thomas Fisher, 23, stabbed 51-year-old Fiona in the horrific attack, with the mother later found after police received a concern for welfare call.

Fisher believed his mum Fiona was trying to destroy him and that she deserved to die.

He crept into her bedroom as she slept and watched over her for 15 minutes before stabbing her in the chest.

The court heard Fisher was in the grip of a delusional mental illness and later told a psychiatrist: “She deserved it and had been bad to me for years. She was destroying me. She wanted me to kill myself.”

At an earlier hearing Fisher denied a charge of murder but pleaded guilty to manslaughter due to diminished responsibility.

Today he was handed a minimum life sentence of two years with a direction he must be treated in a psychiatric hospital until he has recovered and poses no threat to the public.

Lewes Crown Court heard Fisher was once a promising student and a talented guitarist who wanted make a career in music.

With the help of a £50,000 gift from his grandfather, he was able to take up a place at a university in Los Angeles.

But while in the United States he began to use “huge” quantities of cannabis as well as amphetamines, cocaine and heroin.

He ended up dropping out and being flown back to Britain by his family where he continued to smoke cannabis and drink heavily.

While living with his mother he would go shoplifting so that he had money for cannabis and alcohol.

Fisher even twice burgled his mother, stealing her VW Golf and also jewellery and a clock for which he was arrested.

Eventually his mother threw him out and he moved in with his father, Ian, who runs a company offering bespoke services to supercar owners based at Dunsfold Park in Surrey, the home of BBC's Top Gear.

After some months living there his stepmother, Lee Fisher, asked him to leave their home after discovering he had used her iPad to rack up large credit card debts by playing online poker.

Fisher went to live in a hostel in London but continued to suffer mental health problems and was eventually booked into the Priory Clinic after his younger sister, Megan, 20, intervened.

After failing to engage with the treatment programme he left the Priory and eventually went back to living in a hostel.

Shortly afterwards he burgled his mother ’s house and was hauled before the courts and handed a two year suspended sentence and 140 hours community order as well as drugs and alcohol rehabilitation order.

After turning up at his maternal grandparents home in April this year his mum went over and picked him up in her car and drove him back to her home in Crowborough, West Sussex.

The pair enjoyed a day out in Brighton and the following day she took him to an appointment with a senior mental health doctor to organise an assessment.

The day after his sister and grandmother became concerned when they could not contact Mrs Fisher.

Eventually police were called and Mrs Fisher’s body was found lying on a white quilt under her bed. She had been stabbed in the chest with a large wooden-handled kitchen knife.

Fisher, who was dressed in a grey sweatshirt and dark trousers and was flanked by a psychiatric nurse and a dock officer, sat emotionless in the dock as he was sentenced.

Dr Roderick Lay, a consultant psychiatrist said Fisher was most likely suffering from paranoid schizophrenia.

He said his substance abuse had undoubtedly exacerbated his mental health problems rather than been a causal factor.

A statement released on their behalf by police said: "Fiona will be sadly missed by her daughter Megan, her mother Dorothy and stepfather Les, as well as her father.

"There are no words to explain the love those around her felt for her, she is irreplaceable."