A keen footballer and good student, Letts admitted to his parents that he was with ISIS in Syria in September 2014.
The mother of a 20-year-old white British convert to Islam has defended her son who has been dubbed "Jihadi Jack"over fears he had joined the ISIS terrorist group in Syria. Jack Letts left his home in Oxford to travel to the war-torn country a year ago.
His mother, Sally Letts, has insisted that he left for humanitarian purposes rather than terrorism.
The former books editor told the 'Evening Standard', "He is not a member of ISIS; he is very probably not the first white convert that has gone out there. We spoke to him yesterday and he said he had never had a weapon in his hand."
"He went out there for humanitarian purposes to help kids in Syrian refugee camps. It is not as if he is hiding anything - he tells us what he has for breakfast. All this is absolutely ridiculous, it is shocking," she said.
She conceded that the family, based in Oxford, are concerned for Jack's well-being.
"We are worried sick. He is in danger every single moment of the day. He is very naive, very misguided. He wanted to do good in the world and wanted to see for himself. The fact is he did not see the danger or think about his own safety. We wake every single morning not knowing whether he is alive or dead," she told the newspaper.
The family did not oppose Jack converting to Islam, despite them being "pretty well secular" themselves. Jack told his mother and father John, a leading organic farmer, he was planning to travel to Kuwait to study Arabic.
He only informed them he had subsequently gone to Syria once he arrived. He initially worked with refugees and most recently has been helping in a hospital, his family said.
"He repeatedly said he is not with ISIS, and he does not lie. He believes it is un-Islamic to lie and if he does he will go straight to hell, so there is no doubt whatsoever. He has worked in a hospital, done some teaching, done some translating. He is integrated with the population," Sally said.
A Scotland Yard spokesperson said, "What is important, and would be expected, is that we do all we can to keep people safe and investigate everyone who returns to the UK to establish if any crimes have been committed and if they are a threat to the UK".