Inside the mind of Leeds boy whose '˜dark sense of humour' led him to murder his teacher in cold blood

Occasionally in a spot of trouble at school but – behind the moods and growing pains – essentially a loving and caring son.

Fatefully, however, Cornick was hiding what a consultant forensic psychologist would later describe as a “profound state of dissatisfaction with his life and a depressive mind set with negative cognitions”.

That simmering anger would finally boil over to terrible effect on April 28, 2014, when the 15-year-old stabbed his Spanish teacher Ann Maguire at Corpus Christi Catholic College in Halton Moor, Leeds.

Revealed for first time: ‘Red mist’ that drove Leeds pupil to murder his teacher

It remains the only time a teacher has been murdered by a pupil in a UK school.

Today’s report on the findings of a Leeds Safeguarding Children Board learning lessons review into Mrs Maguire’s death reveals that although Cornick was most hostile to those in authority, they were the least able to detect any warning signs about the crime he would eventually commit.

The report says: “A picture emerges of a young person who has been able to compartmentalise his feelings of anger and present ordinarily to his family and within school.”

Cornick, says today’s report, had a happy childhood, with his parents remaining on good terms despite separating in 2001.

He had some difficulties when he started at Corpus Christi yet his head of year commented that he was “a delightful pupil” and, in Year 10, Mrs Maguire wrote: “William is a bright conscientious young man.”

In December 2013, however, the report says Cornick “communicated on social media to a friend about his hatred of Ann and talked about brutally killing her”.

The report also says that, in February 2014, there was a dispute between Cornick and Mrs Maguire over a detention and, later, his parents said his relationship with the teacher had “broken down”. The report says this baffled Mrs Maguire.

Cornick sent another message to a friend on Facebook that Mrs Maguire “deserves more than death more than pain, torture and more than anything that we can understand”.

The report says the teenager decided to murder her four days before he did so. He told other pupils about this and about plans to also kill his head of year and another teacher and her unborn baby.

On the morning of April 28, Cornick packed a rucksack containing a small craft knife and a kitchen knife as well as a bottle of whisky. He intended to give the whisky to a friend “as a ‘parting gift’ after killing Ann”, the report states.

The report then says that, after a “normal” start to the day, Cornick made further statements about what he intended to do. It goes on: “The police investigation highlighted that pupils had heard Will make such statements before and did not take them seriously. One pupil told police that Will had a dark sense of humour.”

During the day’s Spanish GCSE revision lesson, Cornick picked up the larger of the two knives and stabbed Mrs Maguire in the upper back and neck seven times from behind. Teachers and police officers recall that, in the immediate aftermath of the killing, he exhibited a “bizarre calmness and air of normality”.

Cornick was subsequently handed a life sentence for murder and told he must serve a minimum of 20 years in custody before being eligible for release.

An inquest into Mrs Maguire’s death is due to resume following the publication of today’s report - which also reveals the toll that Ann Maguire’s murder took on students and staff at Corpus Christi.

The report says the impact of both her death and the circumstances in which it occurred should not be underestimated. Around 15 former Corpus Christi students are said to have still been showing “obvious signs of trauma” when they started at a local sixth form college in September 2014.

The report’s author, Nick Page, also writes: “Some teachers have spoken to me about their own partners and children being affected and concerned for their welfare when they go to work at the school.”

Mrs Maguire’s family has also called for a full independent inquiry into the circumstances surrounding the murder.

The Leeds Safeguarding Children Board is a statutory body comprising representatives of agencies and organisations including Leeds City Council.