American Muslim convert John Georgelas, the most senior Westerner in Islamic State ranks, was radicalised during a stay in the UK and married a British Muslim, according to reports.

Mr. Georgelas was born into a distinguished American military family. Described as a delinquent who was involved with drugs in his younger years, he converted to Islam at college in Texas following the 9/11 terror attacks.

He turned to radical Islam after moving to the UK, when his father was posted in the 1980s, and having had contact with the infamous “Londonistan” scene. He now works as one of Islamic State’s top recruiters and is reportedly on a U.S. “kill list”.

According to The Sunday Times, Mr. Georgelas married Joya Choudhury, a Briton of Bengali descent, in Rochdale in 2004 when they were both 20. He would eventually persuade her to take their three young boys to Syria while she was pregnant with a fourth child.

The young couple lived in a number of towns during their time in the UK, but it was in London that they became involved with radical Islamic preachers.

Ms. Choudhury is believed to have been radicalised during her A-level studies at a college in East London. Mr. Georgelas had contact with the so-called “Londonistan” scene, which coalesced around Anjem Choudary and his now banned Al-Muhajiroun and Islam4UK groups.

UK authorities and police allowed the scene to flourish for years, choosing to focus on a perceived threat from the “far right”. Mr. Choudary is now imprisoned for recruiting for Islamic State and his organisations have been linked to numerous terror attacks.

After marrying in 2004, Ms. Choudhury and Mr. Georgelas left for Texas, where he was sentenced to 34 months in prison for hacking the website of the American Israel Public Affairs Committee (AIPAC).

In 2011, Mr. Georgelas’ parole expired and the couple moved to Egypt with their two sons, fearing they were under FBI surveillance. In Egypt, they met other European Islamists and Mr. Georgelas made a name for himself as an Islamist “scholar”, The Atlantic reports.

He would later move to Syria to join the newly formed Islamic State. Ms. Choudhury and her children soon became malnourished and seriously ill in the war zone, and they returned to the West.

Ms. Choudhury has now moved to America and settled near Georgelas’s parents, who help to look after the children. In 2014 she filed for divorce.