Media captionJake Petty's mother gave evidence as part of his terror trial, as June Kelly reportsThe mother of a British man who converted to Islam has told a court she begged him not to go to Syria, months before he was killed in battle.
Sue Boyce told the Old Bailey her son told her of his plans only after he left his home in the summer of 2014.
He was killed in battle the same year and Ms Boyce later identified him from video footage, the court heard.
She was speaking at the trial of Lorna Moore and Ayman Shaukat, from Walsall, who both deny terror-related offences.
'Quite horrified'Mr Petty, 25, was one of a group of friends from Walsall, West Midlands, who left Britain in 2014, apparently to join so-called Islamic State.
Ms Boyce said her son, who was brought up in a Church of England family, converted to Islam at about the age of 15, but she had had "no idea" he had thought about travelling to Syria to fight.
In July he flew to Athens and then to Cairo and was initially in contact with his family before going quiet.
Then in late August he called to say he was on Syria's border and would be entering the country as an aid worker.
Image copyrightJulia QuenzlerImage caption[size=0.8125]Sue Boyce told the court she pleaded with her son, Jake Petty, not to go to SyriaMs Boyce said: "I was horrified. I just expressed 'do not be so stupid, don't do it, don't go there'."
The family later received an email, entitled New Life, in which Mr Petty said he had been unhappy living in the UK since he became a Muslim and wanted to be "free to practise Islam".
He told them he had not warned them before about his plan because he thought they might try to stop him.
He wrote: "To live... in a proper Islamic state has been a dream of mine for a long time.
"I did not think I would see it in my lifetime, so I had to rush over here and join my brothers and sisters in Islam as quickly as possible."
Mr Petty said in the email he had been training to become a "soldier".
"Nobody has brainwashed me or tricked me into this, I need to know how to defend myself because the whole world is uniting to destroy us," he added.
Image copyrightWest Midlands PoliceImage caption[size=0.8125]Lorna Moore and Ayman Shaukat deny terror offencesOn 30 October, Ms Boyce contacted MI5 about her son's disappearance after she tried to ring the police but was unable to get through.
Her son had maintained contact with his family through WhatsApp while in Syria, but in the middle of December 2014 all communication ended.
Police visited the family 10 months later with video footage of a dead fighter from Syria and his identity was confirmed.
The trial has heard that others sought to follow Mr Petty and that some of them were helped by Mr Shaukat, 27, of Pargeter Street, Walsall.
Trainee maths teacher Lorna Moore, 33, of Glebe Street, Walsall, denies failing to disclose information about acts of terrorism on or before 24 August 2014 that might have been of assistance in securing the apprehension of her husband, Sajid Aslam.
Mr Shaukat is accused of helping Sajid Aslam and another man, Alex Nash, on their way to Syria.
He denies two counts of preparing for terrorist acts and one charge of possession of a terrorist document.