Western intelligence agencies have been racing to identify Jihadi John since the first video was released by Isis showing the execution of Mr Foley in August.
Unmasking the killer has been a particular priority for US spymasters, who have dispatched extra officials and resources to the UK as part of their efforts.
Speaking earlier this week at the UN in New York, British foreign secretary Philip Hammond said authorities were "getting warm" on identifying the killer.
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Mr Hammond admitted last week, however, that British forces do not know where exactly Isis' hostages are now being held. Isis is currently threatening to execute British aid worker Alan Henning.
A US-led commando raid to rescue hostages held by the militants in July failed after they were moved from their original location in northern Syria.
Jihadi John is said to belong to a clique of British Isis fighters in Syria dubbed "The Beatles" who have been assigned responsibility for guarding hostages by Isis commanders.
The small set of jihadis have been in contact with the families of some of the hostages in the UK in the past and are believed to still have links to their own associates and friends in Britain. Communications between the jihadis have been a particular target for British and US electronic eavesdropping agencies.
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Around 500 Britons are said by security officials to have travelled to Syria to fight for radical militant groups, with most joining Isis.
Many, like Jihadi John, have become embroiled in some of the insurgency's most barbaric activities.
On Wednesday, US officials published the names of two Isis fighters it said were Isis "executioners" – Frenchman Salim Benghalem and Albanian Lavdrim Muhaxheri.
In total, 3,000 European citizens have travelled to the region as mujahideen – a fact that is being seen by EU anti-terror officials as one of the gravest security challenges in decades.
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So far only one terror plot linked to radicals from the conflict in Iraq and Syria has succeeded. In May, Frenchman Mehdi Nemmouche is alleged to have killed four individuals in shootings at a Jewish museum in Belgium. Mr Nemmouche is alleged to have previously fought for Isis in Syria.
The EU's top anti-terror chief, Gilles de Kerchove, warned in an interview with the Financial Times in June that further terror attacks against European states and citizens were inevitable.
Dozens of arrests have taken place across Europe, the Middle East, South Asia and Australia in connection with terror plots linked to Syria and Iraq in recent months.