EPA/IG Jamal al-Harith has been fighting for Islamic State for 18 months, according to sources

Muslim convert Jamal al-Harith, 48, was allowed to travel to Syria unopposed under the cover of carrying out “humanitarian work”. He won the £1million from the last Labour government after saying MI5 helped to have him caged at Guantanamo Bay, in Cuba. It is believed police suspected for six months that he was with IS but feared a public backlash.

GETTY Rebel forces fire at President Assad's troops in Syria

Commons Home Affairs Committee chairman Keith Vaz has called for an inquiry. Web designer al-Harith, from Manchester, was arrested by US forces in Afghanistan after the 9/11 attacks and held for two years. He said he had gone to Pakistan for a “religious holiday” before crossing into Afghanistan and being held by the Taliban. He was released with his £1million in 2004 after saying he had been tortured.

GETTY The aftermath of a missile strike on rebel forces in Syria

GETTY The situation in Syria has become increasingly volatile with Russian military intervention

Then Home Secretary David Blunkett said at the time: “No one who has returned will actually be a threat.”

It’s unbelievable that he’s been allowed to go and fight in Syria without anyone noticing. We have paid him to become a terrorist al-Harith's former neighbour