A gun-obsessed jihadi who claimed to be on the MI5 payroll has been found guilty of having a stash of terror training videos.
Muslim convert Mustafa Abdullah, 34, was stopped at Gatwick Airport last year as he returned from a trip to Syria.
Police examined his phone and computers and uncovered gun instruction videos and audio files on guerilla warfare and combat equipment.
The jury was also shown a photograph from April last year of Abdullah with an automatic rifle on his shoulder, recovered from his mobile.
The appliance engineer, of Binfield Road, Stockwell, south-west London, denied 14 counts of possessing terrorism documents or records and one of possessing a gun for a terrorism purposes.
He told jurors MI5 paid him £10,000 for helping them and insisted he only went to war-torn Syria to do humanitarian work.
However, the jury deliberated for more than 12 hours to find him guilty of 13 offences of possession of documents likely to be useful to a person preparing an act of terrorism. He was cleared of the remaining charges.
He will be sentenced later.
The Old Bailey was told he had an "appalling" criminal past with convictions for wounding and robbery.
It was while he was in jail that he converted to Islam.
Prosecutor William Emlyn Jones said the defendant left one of his Islamic wives, Souriya, around November 2013, intent on martyrdom in the north-west region of Syria where the conflict was intense.
Prompted by the news that some of his "close brothers" had died, Abdullah said he had "set my mind that I want paradise, and paradise is not cheap", the court heard.
Then, in May last year, he made his way back by flying from Turkey to Sweden and then on to Britain.
He was stopped at Gatwick and his phone was seized, leading to the discovery of a large number of videos, audio files and documents on the SD card.
They demonstrated his interest in two things - weapons, specifically firearms and how to use them, and radical, violent and fundamentalist Islamic ideology - "a dangerous mixture".
Abdullah told police at the airport that he was born in the UK of Christian Jamaican parentage but converted to Islam around 2000 and took several wives under Islamic law.
He admitted being in Turkey and Syria but said he went to do aid work in Aleppo and Latakia.
After the phone was examined, Abdullah was arrested in October last year when he claimed that he had not known any of the training videos were on it.
Police also uncovered more material on phones, tablets and a laptop computer at Abdullah's home, jurors were told.
Giving evidence in his defence, Abdullah said he first became involved with the British security service between January and August 2008.
His lawyer Andrew Hill asked: "What was the purpose of the contact?"
Abdullah replied: "Basically, they were saying, 'can you spy for us?'.
"I said Muslims don't spy, however, I will assist you. I don't hang around with people like that but if I do, I will let you know."
Abdullah told jurors he was paid £10,000, adding: "I didn't need the money but they wanted to give it, so I took it."
Three months before he went to Syria, MI5 agent "Graham" called him up and asked for a meeting, but he rebuffed him, the defendant said.
Abdullah, who has several children by various wives, has a previous conviction for possessing documents useful for terrorism.
In September 2006, he was arrested under the Terrorism Act and jailed for two years after pleading guilty at Woolwich Crown Court.
The defendant told jurors of his long-standing fascination with guns, which he compared to his wife's love of handbags.
He said: "My wife said to me, 'it's like I like handbags'. If I was in America I could fire guns all day, no problem. I love guns. I cannot explain it. They look nice."
Abdullah and his wife were photographed on a gun range in the United Arab Emirates and, while working in Yemen in 2012, he bought a gun with a licence.
He told jurors: "You can buy a handgun in the market place like you can buy a cabbage."
But asked if he ever had any intention of harming anybody in this country, Abdullah said: "I'm your local engineer. When I come into your home and fix your appliances, I will make you laugh."