Media playback is unsupported on your device Media caption Daniel Sandford reports on the jihadist who faked his death

A British jihadist who travelled to Syria then faked his own death to try to return to the UK undetected has been given a 12-year custodial sentence.

Imran Khawaja, 27, from west London, joined a militant group with links to so-called Islamic State while overseas.

He was pictured posing with severed heads during his six months in Syria.

He was arrested in Dover last June and later admitted preparing for acts of terrorism, attending a camp, receiving training and possessing firearms.

'Willing participant'

Media playback is unsupported on your device Media caption Commander Richard Walton: Khawaja "was a very serious threat to this country"

Judge Mr Justice Baker said Khawaja posed "a significant risk of serious harm" to the public. He will serve a minimum of eight years and also serve five years on licence.

At Woolwich Crown Court, Khawaja's counsel Henry Blaxland QC told the court his client had a very low IQ and had been "indoctrinated" in the months before he fled for Syria, in January 2014.

But Mr Justice Baker described Khawaja, who joined the Rayat al-Tawheed (RAT) insurgent group, as a "willing and enthusiastic" participant in recruitment films.

And he dismissed Khawaja's claim that he came home to see his family and regretted his actions.

Image copyright PA Image caption Khawaja was a "willing and enthusiastic" participant in recruitment films, the judge said

The judge told him: "It is clear in the last few years you have been showing an increasing interest in Islamic jihadist material.

"You took part in the production of films designed to promote the Islamic State cause and encouraging UK Muslims to join you in jihad.

Imran Khawaja's actions are one of the most appalling examples of violent extremism that I have seen committed by British jihadis Deborah Walsh, Crown Prosecution Service

"Your interest was sufficiently profound for you to travel to Syria to train for jihad.

"I'm also satisfied, by the time you decided to return to the UK, you had completed your terrorist training."

Khawaja showed no emotion as he was led from the court.

His cousin, Tahir Bhatti, from Watford in Hertfordshire was jailed for 21 months. He will serve half of his sentence.

Bhatti had driven to Serbia to collect Khawaja and bring him back to the UK.

Asim Ali, from Ealing in west London - who provided his friend Khawaja with funds - was also given 21 months in prison.

Analysis: BBC home affairs correspondent Dominic Casciani

Imran Khawaja's case is arguably the most serious Syria-related terrorism conviction to date.

Not only is there evidence that he engaged in what the prosecution called "armed activity", but he was part of a social media campaign aimed at recruiting others from Britain - a campaign in which he revelled in the deaths of others.

He could have received a life sentence - but while his extended term is long, it is a slightly shorter term than one given to two Birmingham men who were jailed last year.

Sentencing rules make clear that those who engage in the most serious forms of terrorism can receive terms that are designed to deter others from following them. Khawaja has the rest of his life to think about what he did - and he has told the court that he hopes other men do not make the same mistake.

Messages from Khawaja's family were read to the court on Thursday.

In them, he lied about when he was coming home from Syria, before confiding he was there to die a martyr.

The court saw a video of Khawaja posing with severed heads in the Middle East country.

Dozens of images of him posing with automatic weapons and tanks were also produced.

The court was also told of social media postings about his apparent death after a fake announcement was made on social media site Instagram.

Prosecutor Brian Altman said the postings provided cover for Khawaja's return to the UK on 3 June.

Image caption Khawaja was pictured with weapons and severed heads

Crown Prosecution Service deputy head of counter terrorism Deborah Walsh said: "Imran Khawaja's actions are one of the most appalling examples of violent extremism that I have seen committed by British jihadis returning from Syria.

"Photos and videos of Khawaja posing with child soldiers and severed heads defy the understanding of civilised people and paint a picture of a man who would stop at nothing to spread terror and hatred.

"It is clear from the evidence that he went to Syria to train and to fight, and was close to, if not directly in, a combat zone."

'Crimes against humanity'

Metropolitan Police Commander Richard Walton said images and video of Khawaja in Syria were "horrific and deeply disturbing".

Speaking after the sentencing, he said: "Khawaja chose to become a terrorist, engaged in weapons training in a terrorist training camp and faked his own death in order to conceal his entry back into the UK.

"This sentence sends a powerful message to those who plan or prepare acts of terrorism overseas or here in the UK.

"We have seen how parts of Syria have become lawless, where murder, torture and crimes against humanity are becoming almost routine. One of the best ways we can respond to these crimes is to convict terrorists through the rule of law."