A report has detailed how an "intelligent and ambitious" 16-year-old girl from Tower Hamlets was radicalised to join Islamic State (Isis) after becoming immune to harrowing execution videos.

The girl, known as 'B', was taken away from her family in August 2015 after she tried to flee to Syria. Met Police swooped to take her off a plane at Heathrow Airport in December 2014 after her younger brother told their mother she was travelling to the civil war-torn country.

She was later allowed to return to her family home in East London – where she lived with her parents and five brothers and sisters – before Counter Terror police arrested her and the family under the Terror Act.

The mother, father and siblings were released without charge but 'B' – who confirmed to police she followed an Isis ideology and wanted to travel to Syria to "live in an Islamic state under Sharia law" – was made a ward of court and moved to Telford.

A High Court judgement published on Thursday (14 July) reveals the factors that led to her radicalisation including downloading Isis propaganda showing mass executions. The report also blames the girl's parents for either holding extremist views or for failing to spot her fundamentalism, and highlighted how neither the parents nor B would give evidence at the hearing last year.

Mr Justice Hayden said the escalation in violence in Gaza in the summer of 2014 triggered her radicalisation and that he put her in local authority care to try to "reassert" her mind.

"What she needs, I find, is to be provided with an opportunity in which she can, in a peaceful and safe situation, be afforded the chance for her strong and lively mind to reassert its own independence," Hayden said in his August 2015 judgement.

"An environment in which there are the kind of vile images that I have described and the extreme polemic I have outlined, can only be deleterious to her emotional welfare. I hope she can be provided with an opportunity where her thoughts might turn to healthier and I hope happier issues."