The parents of a teenage Muslim convert bought him a plane ticket to the Middle East for a “grand adventure”, despite being warned that he was radicalised and wanted to fight in Syria.

The Old Bailey heard that Jack Letts’s parents had been “supportive” when he converted to Islam aged 16 in Oxford.

Sally Lane, 56, and John Letts, 58, later helped him travel to Jordan and allegedly tried to send him more than £1,700 after he reached Isis territory.

The defendants, of Chiswell Road in Oxford, deny three charges of funding terrorism.

But opening the case on Wednesday, prosecutors said they “knew or had reasonable cause to suspect” their son had joined Isis in Syria and had been warned about his activities and the consequences of their alleged actions.

Timeline of the Isis caliphate Show all 19 1 /19 Timeline of the Isis caliphate Timeline of the Isis caliphate ISIS began as a group by the merging of extremist organisations ISI and al-Nusra in 2013. Following clashes, Syrian rebels captured the ISIS headquarters in Aleppo in January 2014 (pictured) AFP/Getty Timeline of the Isis caliphate Abu Bakr Al-Baghdadi declared the creation of a caliphate in Mosul on 27 June 2014 Timeline of the Isis caliphate Isis conquered the Kurdish towns of Sinjar and Zumar in August 2014, forcing thousands of civilians to flee their homes. Pictured are a group of Yazidi Kurds who have fled Rex Timeline of the Isis caliphate On September 2 2014 Isis released a video depicting the beheading of US journalist Steven Sotloff. On September 13 they released another video showing the execution of British aid worker David Haines Timeline of the Isis caliphate The US launched its first airstrikes against Isis in Syria on 23 September 2014. Here Lt Gen William C Mayville Jnr speaks about the bombing campaign in the wake of the first strikes Getty Timeline of the Isis caliphate Isis militants sit atop a hill planted with their flag in the Syrian town of Kobani on 6 October 2014. They had been advancing on Kobani since mid-September and by now was in control of the city’s entrance and exit points AFP/Getty Timeline of the Isis caliphate Residents of the border village of Alizar keep guard day and night as they wait in fear of mortar fire from Isis who have occupied the nearby city of Kobani Getty Timeline of the Isis caliphate Smoke rises following a US airstrike on Kobani, 28 October 2014 AFP/Getty Timeline of the Isis caliphate YPG fighters raise a flag as they reclaim Kobani on 26 January 2015 VOA Timeline of the Isis caliphate Isis seized the ancient Syrian city of Palmyra on 20 May 2015. This image show the city from above days after its capture by Isis Getty Timeline of the Isis caliphate Kurdish forces are stationed on a hill above the town of Sinjar as smoke rises following US airstrikes on 12 November 2015 AFP/Getty Timeline of the Isis caliphate Kurdish forces enter Sinjar after seizing it from Isis control on 13 November 2015 AFP/Getty Timeline of the Isis caliphate Iraqi government forces make the victory sign as they retake the city of Fallujah from ISIS on 26 June 2016 Getty Timeline of the Isis caliphate Iraqi forces battle with Isis for the city of Mosul on 30 June 2017 AFP/Getty Timeline of the Isis caliphate Members of the Iraqi federal police raise flags in Mosul on 8 July 2017. On the following day, Iraqi prime minister Haider Al Abadi declares victory over Isis in Mosul Getty Timeline of the Isis caliphate Members of Syrian Democratic Forces celebrate in Al-Naim square after taking back the city of Raqqa from Isis. US-backed Syrian forces declare victory over Isis in Raqqa on 20 October 2017 after a four-month long campaign Getty Timeline of the Isis caliphate Female fighters of the Syrian Democratic Forces celebrate in Al-Naim Square after taking back the city of Raqqa from Isis. US-backed Syrian forces declare victory over Isis in Raqqa on 20 October 2017 after a four-month long campaign AFP/Getty Timeline of the Isis caliphate Trucks full of women and children arrive from the last Isis-held areas in Deir ez-Zor, Syria in January 2019 They were among the last civilians to be living in the ISIS caliphate, by this time reduced to just two small villages in Syria’s Deir ez-Zor Richard Hall/The Independent Timeline of the Isis caliphate Zikia Ibrahim, 28, with her two-year-old son and 8-month-old daughter, after fleeing the Isis caliphate, on Saturday 26 January 2019 Richard Hall/The Independent

Alison Morgan QC told the jury that members of an Oxford mosque Jack attended initially thought he was “curious about Islam and keen to learn”.

“But he then came into contact at the mosque with men who appeared to introduce him to a more radical ideology,” she added.

“Jack began to express himself in more extreme language and he appeared to have been radicalised by others.”

One of the teenager’s friends from the mosque, Anwar Belhimer, contacted Mr Letts in May 2014 because Jack had told him of plans to travel to Kuwait.

The court heard that he “urged Mr Letts to stop his son from travelling and to confiscate his passport”, warning that he had been saying “worrying things”.

Ms Morgan said that at a meeting with Jack and his father, Mr Belhimer “pleaded with Jack not to travel, saying that there were other ways that he could help the people of Syria rather than by going out to fight”.

“Mr Belheimer’s engagement with John Letts was a clear warning to the defendants about Jack’s radicalisation and his intentions, before he even left this country,” the prosecutor added.

“Despite the concerns that had been expressed to them about Jack’s potential radicalisation, and against the background of their own concerns about Jack’s emotional wellbeing, the defendants permitted Jack’s travel.”

On 24 May 2014, Ms Lane bought a ticket from London Heathrow to the Jordanian capital of Amman, and Jack – who was then 18 – flew out two days later.

The court heard that a return flight was booked for June, but never used.

Jack Letts left the UK aged 18 in 2014 (ITV News)

Prosecutors showed the jury an email where Ms Lane told a friend she had been stressed about “Jack saying he was going to fight in Syria”, but had then told his parents he had “decided not to fight”.

“You may want to consider why, if she thought that there was any possibility of Jack going to fight in Syria, she decided to pay for his flight nonetheless,” Ms Morgan told jurors.

The court heard that analysis of phones seized from the family home suggested that Jack remained in Jordan until September 2014 and it “became clear” that he would not be using his return ticket.

He initially told his parents he wanted to travel to Kuwait and they discussed the plan in “happy exchanges”.

The jury was read an email from Mr Letts to his son reading: “Hi bud. It’s weird emailing you so far away but hey, you’re on a grand adventure.”

Jack’s parents sent him money transfers totalling £350 in Jordan and £900 at a location where they “understood him to be” in Kuwait.

They are not charged with a criminal offence over those funding because Jack was not yet in Iraq or Syria, but prosecutors said he was “about to travel into Islamic State territory”.

Ms Morgan told the jury of “clear warning signs about what Jack was doing”, including a message from an Oxford PhD student with links to Kuwait raising concerns about the “company he is keeping”.

Mr Letts wrote in an email that he was “not getting much info back from him”, until Jack asked for money to leave Kuwait in August 2014.

Phone records from the following month show Jack was in Turkey, the court heard, and the “tone of communications changed”.

Mr Letts emailed his son saying: “Jack, a father should never live to see his son buried. Please, I beg you my son, come home or at least leave where you are and do not get so involved … there are many other things you can do to help and carry out Allah’s will.”

The trial is under way at the Old Bailey in London (Getty)

He said that Ms Lane was “collapsing with fear and sadness”, writing: “You have misled us. You were supposed to be studying in Kuwait. Where are you? What are you doing?”

Mr Letts added: “You don’t have to die to help your fellow Muslims.”

He later told the Oxford academic who raised concerns that Jack was not in Kuwait and had “gone to a more radical place”.

The court heard that Ms Lane contacted a man called Dewan Musa, who she described as being “one of Jack’s most militant friends” from the mosque.

In September 2014, she wrote to Musa: “I believe my son received help from people from Portsmouth to travel to a warzone.”

The court heard that Ms Lane later obtained Facebook messages between Jack and Musa by accessing her son’s account and concluded that the man was “obviously a fighter, perhaps he is the one who helped him”.

Excerpts of the conversation read to the jury that Jack and Musa had discussed Isis’s goals and a “path”.

“We suggest the path being talked about was the route to get into Islamic State territory and that is what Musa was assisting Jack to do,” Ms Morgan told the court.

“It was in this period that Ms Lane was making money transfers to Jack … all of this would have become apparent to Ms Lane when she captured the conversation and studied it. She was aware of what he’d done, plans he’d made with Dewan and that the money was not being used for study.”

Ms Morgan told the jury that Ms Lane and Mr Letts were not alleged to be terrorists or have sympathies for Isis themselves.

“However, they sent money to their son, with knowledge or reasonable cause to suspect that it might be used by him or others to support terrorist activity,” she added.“The law is focused on the greater good, stopping money flowing into terrorist groups.”

Ms Morgan accused the parents of committing terror offences “despite being warned by a wide variety of people: those who had associated with Jack Letts before he travelled, academics who told the defendants what to do and not to do who they had sought out for advice, a charity worker who advised them as to how they might encourage their son to come back from Syria”.

“It was not open to these defendants to take the law into their own hands and to send money to their son, whatever their own reasons and motives may have been,” she added.