Media playback is unsupported on your device Media caption Daniel Sandford explains how Junead Khan's plot was exposed

A delivery driver from Luton has been convicted of plotting to kill a US airman outside a base in East Anglia.

Junead Khan, 25, a supporter of so-called Islamic State (IS), was found guilty of preparing terrorist acts.

Khan had driven past RAF Lakenheath and other US bases on his delivery route, and had discussed staging a car crash and attacking a soldier with a knife.

He was also convicted of preparing to join IS in Syria. His uncle Shazib Khan was also convicted of the same charge.

In what police called a "chilling message" to a suspected IS member, Junead Khan described how he had missed an opportunity to kill US soldiers on his rounds as a delivery driver.

The message said: "When I saw these US soldiers on road it just looked simple but I had nothing on me or would've got into an accident with them and made them get out the car."

His contact replied: "That's what the brother done with Lee Rigby" - referring to the British solider murdered in Woolwich in 2013.

'Embroiled in extremism'

During the trial, the court heard Junead Khan had been identified under the government's anti-extremism programme - and had mocked it after police visited him in 2014.

He sent a message to his 23-year-old uncle, Shazib, also from Luton, saying he was laughing out loud because police left a card asking him to call them.

He later met with officers and afterwards sent a message saying: "Hopefully the last I hear from them."

Image copyright Met Police Image caption Shazib Khan is Junead Khan's uncle, and two years younger than he is

Commenting after the verdicts, police said Junead Khan "repeatedly rejected police offers to help divert him from radicalism".

Officers working as part of Prevent - the government's drive to stop people becoming terrorists or supporting terrorism - visited him four times in 2014, the Metropolitan Police said.

But he refused help and became "more embroiled in extremism", and after his arrest police found material including "bomb making guides and terrorist propaganda".

Commander Dean Haydon, of the Metropolitan Police's Counter Terrorism Command, said Junead Khan had done extensive research on how to make a bomb.

Police also recovered British and US flags stolen from a diner in Dunstable. These were "potentially to be used for a symbolic act during the terrorist attack", the Met said.

In July 2015, Junead Khan had an encrypted online conversation with Junaid Hussain, a British IS operative in Syria.

Image caption The US military said Junaid Hussain's online activity meant he could "reach across the sea" to inspire violence

He was sent instructions on how to build a bomb and was told to use it against police if they arrived on the scene of his planned attack.

Days after this online conversation he carried out internet research into buying a large knife - but was then arrested at his workplace.

The following month Junaid Hussain was killed in a US missile strike - one of only a few British IS operatives who have been targeted in this way.

Hussain was a hacker and IS propagandist, and US military spokesman Colonel Steve Warren said he had the potential to "radicalise and inspire violence in foreign countries around the world".

Sue Hemming, head of the counter terrorism division of the Crown Prosecution Service, said: "Through early detection and prosecution of these individuals more serious crimes have been avoided which could have had devastating consequences in the UK or Syria."

The verdicts came after a six-week trial at Kingston Crown Court.

The men were remanded in custody and will be sentenced on 13 May.