A teenager who made bogus bomb threats that triggered the evacuation of more than 400 schools has been jailed for three years.

George Duke-Cohan, 19, sent thousands of e-mail warnings in March.

Kent Police was made aware of the messages and treated them as a hoax.

The National Crime Agency has released a video of Duke-Cohan's arrest following the sentencing.

Duke-Cohan, from Watford, had admitted making bomb threats to thousands of schools, including a number in Kent.

Luton Crown Court also heard how he caused a security scare with a phone call to an airport.

A United Airlines plane was quarantined when it arrived at San Francisco airport, with all 295 passengers kept on board for eight hours while a security investigation took place.

Duke-Cohan, 19, pleaded guilty to three counts of making hoax bomb threats at the court in September following an investigation by the National Crime Agency (NCA).

He sent the bomb threats in March and was arrested just days later.

In April whilst under investigation, he sent a mass email to schools in the UK and the US claiming that pipe bombs had been planted on the premises.

On 9 August, the hacker group known as ‘Apophis Squad’ claimed on their Twitter page that flight UAL 949 had been grounded due to their actions.

“He carried out these threats hidden behind a computer screen for his own enjoyment, with no consideration for the effect he was having on others." - NCA officer Marc Horsfall

NCA investigators working with the FBI identified that whilst on bail for the threats to schools, Duke-Cohan made bomb threats to the US-bound flight via phone calls to San Francisco Airport and their Bureau police.

In a recording of one of the phone calls which was made while the plane was in the air, he takes on the persona of a worried father and claims his daughter contacted him from the flight to say it had been hijacked by gunmen, one of whom had a bomb.

On arrival in San Francisco the plane was the subject of a significant security operation in a quarantined area of the airport.

All passengers had to remain on board causing disruption to onward journeys and financial loss to the airline.

In an operation supported by Hertfordshire Police, Duke-Cohan was arrested by NCA officers for the third time at his home in Watford on August 31.

Officers recovered multiple electronic devices belonging to him, the use of which was in contravention to his bail conditions imposed on him.

NCA senior investigating officer Marc Horsfall said: “Duke-Cohan made a series of bomb threats that caused serious worry and inconvenience to thousands of people, not least an international airline.

“He carried out these threats hidden behind a computer screen for his own enjoyment, with no consideration for the effect he was having on others.

“Despite being arrested and having conditions imposed restricting his use of technology, he persistently broke those conditions to continue his wave of violent threats.

“Law enforcement take such offences extremely seriously. The sentence handed down to Duke-Cohan today highlights the consequences of such offending.

“This investigation proves that operating online does not offer offenders anonymity. Duke-Cohan now has a criminal record which will harm his future career prospects and this should act as a deterrent to others.”