A teenager who threw a six-year-old boy off a Tate Modern viewing platform has been jailed for life.
Jonty Bravery, now 18, will serve at least 15 years in prison for attempted murder and may never be freed.
A judge said the horror and fear felt by the young victim and his parents, who were standing nearby at the time, were “beyond imagination”.
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“You choose a small child because of his vulnerability,” Mrs Justice McGowan said. “You had intended to kill someone that day – you almost killed that six-year-old boy.”
She said Bravery’s autism and personality disorder did not explain the attack, and that expert evidence indicated he presents “a grave and immediate danger to the public”.
“You will spend the greater part – if not all – of your life detained … you may never be released,” the judge told Bravery as she jailed him on Friday.
He had attempted to enter the Shard – the UK’s tallest skyscraper – before heading to the art gallery on 4 August last year.
The Old Bailey heard that the victim and his parents, who were French tourists on holiday in the UK, entered the 10th floor viewing platform minutes after Bravery.
CCTV footage showed him turning towards the victim’s family as the boy skipped a little way away from his parents.
“As [the boy] approached, the defendant scooped him up and, without any hesitation, carried him straight to the railings and threw him over,” said prosecutor Deanna Heer.
“The CCTV footage shows him falling head-first towards the ground.”
Bravery, from Ealing in west London, then sought out Tate staff and confessed: “I think I’ve murdered someone, I’ve just thrown someone off the balcony.”
The boy fell five storeys before landing on a roof, and was left with life-changing injuries.
He remains in a wheelchair with constant care, and it is not known whether he will make a full recovery.
Ms Heer said the victim was “fortunate not to die”, adding: “This was a whisper away from a murder.”
In a victim impact statement, the parents said they had not felt able to leave their son’s side for more than a couple of hours because they are “so scared of losing him”.
“The act committed by this defendant against our son is unspeakable,” they added, saying their son was unable to trust people and “would like to slap” Bravery for what he did.
Bravery sat with his T-shirt pulled over his head, then crouched on the floor with his back to a videolink camera as details of the case were read out at the sentencing hearing.
The teenager, then 17, was seen backing away from the railings while smiling and appearing to laugh immediately afterwards.
When challenged by the father, Bravery told him he was “mad” and witnesses described him having a “big smile on his face”.
He was also heard to say “it’s not my fault, it’s social services’ fault” and asked police if he was going to be on the news after being arrested.
Bravery said that he had been “seriously unhappy” and “hearing voices” telling him to hurt and kill people for months before the attack.
The court heard he had planned the offence “well in advance” and researched the easiest way to kill someone.
Ms Heer said Bravery had conducted a variety of searches including, “are you guaranteed to escape prison if you have autism?”, “what are the chances of death if you push into the River Thames?” and a web page entitled “how to get away with rape”.
The prosecutor added: “He narrowed it down to three possibilities: strangling a woman or a child, drowning a child or throwing someone off a tall building.”
Bravery told medical experts he felt “indestructible” and “on top of the world” after throwing the boy from the viewing platform.
He was under the care of Hammersmith and Fulham social services at the time, and living in supported accommodation.
Bravery was described as abusive and aggressive towards staff, and assaulted a female care worker in 2017.
At the time of the attempted murder, he was under one-on-one supervision but was allowed to go out unaccompanied for four-hour periods.
The court heard that Bravery has autism spectrum disorder and a personality disorder, both of which are relevant to understand his behaviour.
A recording, taken by one of Bravery’s care workers in autumn 2018, suggested opportunities to stop the attack were missed.
“In the next few months I’ve got it in my head I’ve got to kill somebody,” he could be heard saying, describing his urge to push someone off a building in central London.
“It could be the Shard, it could be anything just as long as it’s a high thing and we can go up and visit it and then push somebody off it and I know for a fact they’ll die from falling from a hundred feet.”
The former care worker who took the recording told the BBC Bravery had mentioned similar plans several times, adding: “There were a few incidences regarding trying to hurt people, life-wrecking incidences that he had planned in his head.”
Mrs Justice McGowan said Bravery had been described as “callous” by psychologists, adding: “You planned this, you worked out which buildings you might try, based on height and cost of admission and you appear to have revelled in the notoriety.”
Bravery told police he had to prove a point “to every idiot” who said he had no mental health problems, saying he wanted to be on the news “so when it is official no-one can say anything else”.
In a series of social media posts before the attack, which have since been deleted, his father Piers Bravery attempted to raise awareness of autism and urged the health secretary to “do your job and stop more children dying“.
Defence counsel Ms Philippa said it was “unlikely” her client, who was diagnosed with autism spectrum disorder when he was five, would ever be released into the community.
“There’s no immediate cure for this defendant’s condition,” she added. “We’re talking about this young man in whichever setting – either hospital or prison – for a very, very long period.”
Hammersmith and Fulham Council said an independent serious case review was underway.
Additional reporting by PA