A student who wanted to fly an Islamic State flag over Downing Street has been found guilty of planning to join rebels in Syria.
David Souaan, 20, began to cry when the judge warned him jail is inevitable when he is sentenced in the new year.
He was accused of preparing for terrorist acts in Syria around the time he was stopped at Heathrow Airport on May 31.
The prosecution said he had visited in December last year, and was on his way back to fight the jihadist cause when he was arrested.
The Birkbeck College student, who comes from a wealthy family in Serbia, denied this and insisted his earlier visit to Syria was to collect his grandfather's belongings.
He claimed he posed for pictures with guns because he wanted to look "cool".
A jury took nine hours to find him guilty following a trial at the Old Bailey.
Remanding Souaan in custody, Judge Peter Rook said: "You have been convicted of a very serious offence indeed. You must understand that you will be receiving a custodial sentence in this case."
Souaan came to the UK in 2013 on a three-year visa to study global politics and international relations at Birkbeck College in London.
He was arrested after fellow students became concerned at his radical views on Islam and he had shown off pictures of himself posing with guns.
Police seized his laptop and iPhone and found a mass of pictures, videos and documents revealing his "extremist sympathies" and that he had not only been fighting in Syria before but was intending to return, the Old Bailey heard.
Prosecutor Sarah Whitehouse QC said one video clip on his iPhone was "so graphic and so shocking" that it could not be played in court.
It featured a man kneeling with his head held back as another man cut his throat.
The court heard that Souaan filmed himself attending a demonstration in the UK.
In the background, a man can be heard to say: "The flag of Tawheed in London, all praise be to Allah the lord of the universe."
This was in reference to the wish of Muslim extremists to see the black flag fly over Downing Street.
Sentencing was adjourned until 3 February for pre-sentence reports.