The mother of a Muslim convert dubbed “Jihadi Jack” told a court she was “horrified” when he called to say he was in Syria.

Sally Lane, 56, and her husband are accused of sending or trying to send her son £1,723, despite having reason to believe he had joined Islamic State.

Jack Letts left his Oxford home at 18, married an Iraqi tribesman’s daughter and moved to Syria, jurors have heard.

Mrs Lane and John Letts, 58, deny three charges of funding terrorism. They are alleged to have ignored repeated warnings that they faced prosecution if they tried to help their son while he was in IS territory.

Giving evidence at the Old Bailey, Mrs Lane told jurors her son had initially gone to Jordan and Kuwait for study and tourism.

She said: “He seemed like he was enjoying himself, relaxing and enjoying the country.”

But on 2 September 2014, phone records showed a flurry of calls.

Lane said: “That was the day I found out. Jack phoned me. I was alone in the house. It was just a very quick phone call. He said ‘Mum, I’m in Syria’. “I was horrified. I screamed at him, ‘How could you be so stupid? You will get killed. You will get beheaded’.”

Jack Letts, who is said to suffer from obsessive compulsive disorder, did not phone again until 24 September 2014. Mrs Lane said: “He did not say exactly where he was. He tried to be reassuring, saying everything is fine. It’s a civilian area, it’s not a war zone.”

Defence lawyer Tim Moloney QC asked: “How did all that contact make you feel?” She replied: “We did not know whether he was alive or dead. At least we were reassured he was alive.”

A month later, Mrs Lane attempted to use a £5,000 inheritance from her son’s grandfather “as a bribe” to encourage him and his new wife Asmaa to get “somewhere safe”.

The trial continues.