Sevenoaks primary school assistant jailed for stabbing ex-girlfriend's parents Luke Nicholson, 29, received 16-year jail sentence for grievous bodily harm He attacked father on doorstep, mother in living room, his ex in the garden Ex Cheryl Slim, 30, did not realise who it was until she was being strangled Judge Stephen Waller said he had 'no clue' why he launched his attack Jailed: Luke Nicholson, 29, waded past Cheryl Slim's parents with knives to strangle their daughter A 'mild-mannered' primary school assistant who stabbed his ex-girlfriend's parents before strangling their daughter during a horrific suburban nightmare has been jailed. Luke Nicholson, 29, who had never been in trouble with the police before, attacked Cheryl Slim's father on the doorstep of her family home, before slashing her mother in the living room, and trying to strange his former girlfriend in the back garden. Schoolteacher Cheryl, 30, who broke up with Nicholson five years ago, tried to escape from the upstairs bathroom window but was accosted by her attacker when she fell. She did not realise it was her former boyfriend until he was strangling her. Struggling for breath, she tried to play dead but Nicholson only released his grip and fled when the next-door neighbour smashed through the garden fence to stop him. Nicholson, of Sevenoaks, Kent, who assisted primary school children with special needs, pleaded guilty to three counts of grievous bodily harm with intent, in relation to Robert Slim, 59, Annette Slim, 55, and Cheryl on January 24. The prosecution found the defendant had attempted to make Facebook contact with his ex of five years, and made other internet searches for her in the period before the attack. Croydon Crown Court was told the defendant rode his moped twenty miles in the snow, buying the knives from Tesco's on the way. He ended up outside the Slim's family home in Beckenham, where he once spent Christmas years before. Mr Slim described Nicholson as having a 'vacant, emotionless expression' when he answered the door to him. He was stabbed in the upper arm without warning - slashing his artery - and sustained further injuries as they fought in the hallway. Traumatised: Attack victims Cheryl Slim, 30, and her father Robert Slim, 59, leave Croydon Crown Court Victims: Mr Slim was stabbed in the artery and his wife Annette, 55, was stabbed in the hand by Nicholson Mrs Slim emerged from the living-room, where the couple had been watching television, and smashed Nicholson over the head with a plant pot several times without effect. 'He turned his attention to Mrs Slim and she tried to grab the knife from his hand,' explained prosecutor Mr Patrick Moran. In the ensuing struggle the defendant lashed out at her several times with the knife. She suffered severed tendons to one of her hands as she successfully prized the knife from Nicholson, who then began hunting the house for Cheryl, leaving a trail of bloody footprints up to the bathroom, where she had locked herself in. 'Fearing that someone would break through the bathroom door to find her she opened the bathroom window and climbed out of it,' added Mr Moran. The window overlooked the back garden and it was into that garden Miss Slim fell as she tried to lower herself from the edge. No sooner had she got up than the defendant tackled her back to the ground and smashed a hard object against her head - possibly a garden ornament. The defendant then dragged Miss Slim down to the end of the garden, further from her parents, who had no idea that the defendant had her, quite literally, in his grip. She struggled on the ground underneath the defendant as he gripped her neck and it was only at that stage that she believed she recognised her attacker as a former boyfriend. Home: The family home, where Nicholson spent Christmas five years ago. A neighbour intervened mid-attack 'She was struggling to breathe as she felt her windpipe being crushed and sought to defend herself by clawing at the defendant's face. Miss Slim could do little more to defend herself, as she felt as if she was losing consciousness, and decided to stop struggling and lie still. After the neighbour disturbed the heavily bloodstained Nicholson he made his way back through the blood-splattered house, past Mr Slim, who had collapsed on the kitchen floor from excessive bleeding, and out the front door. Police stopped him a few street away and an obviously drunken Nicholson said: 'I don't know what you are talking about,' with officers describing him as being in an 'agitated' state. Miss Charlotte Newell, defending, said: 'What led this mild-mannered, gentle young man to behave this way may never be clear. His family are devastated by the havoc that has been wreaked. His actions do not square with the young man the family raised. The court heard Nicholson attended London Metropolitan University, which recently awarded him a diploma and Miss Newell added: 'His true nature was not on display that evening. Sentence: Nicholson pleaded guilty to three counts of grievous bodily harm at Croydon Crown Court yesterday His relationship with Miss Slim did not end well, but he did not bear her any ill will and even though she had been on his mind this exploded from nothing. There is no real grudge against the Slim's.' Judge Stephen Waller heard Nicholas had abused alcohol and cannabis throughout his adult life and said: 'I think he poses a risk to any person with whom he has a grievance while under the influence of drink and drugs. 'There was carnage in the hallway of that suburban house,' he added. This was a premeditated sustained attack on three defenceless people in their own home. They will find it difficult, if ever, to recover from such a horrifying experience. There is nothing in your background that gives any clue as to why you acted in that dreadful fashion that night. The probation service found there was a 'high likelihood' that Nicholson would re-offend and a restraining order was made to protect the Slim family once he is paroled. Judge Waller told Nicholson he would have to serve at least two-thirds of the sentence and would be subjected to an extended licence period of an additional five years.