Mentally ill teenager Jonty Bravery "was seen laughing" moments after throwing a six-year-old boy from a high viewing platform at London's Tate Modern last year.

Listening to an account of the shocking incident, a court heard how Bravery told onlookers "it's not my fault it's social services' fault" recently.

Bravery, who was 17 at the time and is now 18, has admitted attempted murder.

He was said to "have a big smile on his face" and told the boy's father: "Yes I am mad," in the immediate wake of the incident.

The Old Bailey heard how Bravery spent more than 15 minutes stalking possible targets at the art gallery viewing platform before fixing on a young visitor who had briefly left his parents' side.

The teenager, who is from Ealing, was said to have "scooped (the victim) up and, without any hesitation, carried him straight to the railings and threw him over".

Wandsworth Times: The Tate Modern viewing platform. Image: © Copyright Rod Allday via Tate Modern viewing platform. Image: © Copyright Rod Allday via

The child's mother soon became "increasingly hysterical" and tried to climb over the railings to get to her son several stories below, but was held back by staff, the court heard.

Attendees at the trial were told Bravery was under one-on-one supervision with Hammersmith and Fulham Social Services at the time of the attack on August 4, but was allowed to go out unaccompanied for four-hour periods.

Prosecutor Deanna Heer told Bravery's sentencing hearing on Thursday (June 25) that CCTV captured the incident, then showed the defendant backing away from the railings.

She said: "He can be seen to be smiling, with his arms raised. At one point, he appears to shrug and laugh."

The six-year-old boy who Bravery threw from the building suffered injuries that might have killed him, and spent more than a month in hospital in the UK before being discharged to a hospital in France.

A nurse from Surrey previously helped raise tens of thousands of pounds for his care online. 

He and his family had been visiting the UK from France when the attack happened.

He remains in a wheelchair, and will reportedly require 100 per cent care support until at least August 2022.

Bravery said he had been planning the incident for a long time, the court was told.

Giving evidence, Dr Joanna Dow, a consultant forensic psychiatrist who works at Broadmoor Hospital where Bravery is being held, said she believed the defendant had a mixed personality disorder and struggled to manage his emotions.

She recommended Bravery be detained in hospital, rather than handed a prison sentence, so he could get treatment such as anger management and to learn social communication and interaction skills.