British Special Forces hunting the killer of James Foley are using an array of sophisticated equipment to track him down – and possibly free other hostages being held.

The Mail on Sunday has been given a detailed account of how elite troops from the SAS and the Special Reconnaissance Regiment (SRR) are conducting high-tech operations inside Syria and Iraq, which could lead to the capture of the extremists within days.

It emerged as reports suggested that British intelligence services had identified the true identity of the terrorist who beheaded Mr Foley – as seen in a video which shocked the world - known as 'Jihadi John'.

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The SAS team tasked with hunting down the ISIS terrorists will use hand-launched surveillance drones

Elite force: The SAS are experts in desert warfare having conducted operations in the Middle East for decades. Pictured are a heavily armed British Special Forces patrol in Afghanistan in 2001

The Mail on Sunday has been told that in the past 48 hours a ‘significant force’ of SAS soldiers and signallers have deployed to northern Iraq, joining Iraqi and Kurdish units fighting IS.

They have separated into four-man teams and are accompanying local troops in an attempt to capture British jihadis, identify them and establish links to Jihadi John.

A key suspect is 23-year-old Abdel-Majed Abdel Bary, who until a year ago lived with his family in their £1m home in the affluent London area of Maida Vale, but recently appeared on social media grasping a severed head, an anonymous government source told The Sunday Times.

Once a British jihadi is in custody, samples will be taken of the suspect’s blood and DNA – vital in the case of UK extremists because the information can be matched to medical records. For identification purposes, a photograph is also taken of the iris – the visible coloured ring around the pupil – which is unique.

One SAS source said: ‘It is possible to identify British jihadis on the battlefield by intercepting their radio messages. When they’re captured by the Iraqis or Kurds we’ll take a close interest in their questioning.

‘Gathering information such as their blood group and DNA, as well as voice recordings in either Arabic or English, will help us zero in on Jihadi John because it can be compared with existing data.’

Public Enemy Number 1: The SAS have been ordered to find out the British born terrorist 'Jihad John'

From the battleground this information is sent via a portable satellite manned by a soldier from 264 (SAS) Signal Squadron, who beams it to a spy plane, such as the ‘Rivet Joint’ aircraft, circling overhead.

Inside Rivet Joint, a 17-man team processes the information and sends it back to GCHQ, the Government’s secret communications headquarters at Cheltenham. Here it is analysed and matched against records of British jihadis believed to be fighting in Syria and Iraq, before ‘feedback information’ is sent to SAS teams.

GCHQ’s library is believed to include recordings of thousands of voices taken from phone and radio intercepts. Meanwhile, on the Turkish-Syrian border, SRR soldiers fly drones into IS strongholds and give live details of their movements.

Such a detailed study of their bases is intended to prevent a repeat of the US Special Forces mission last month which failed to find any hostages. American Delta Force troops raided an IS base at Uqayrishah in northern Syria, but were forced to retreat after a gun battle with terrorists.

The SRR’s drones can fly for up to 24 hours, climbing to an altitude of more than 18,000ft. From here they are able to survey hundreds of miles of territory occupied by IS fighters, including the city of Raqqa, where it is believed several Western hostages have been held.

Intelligence gathered will be used in the planning stages ahead of any incursion by SRR troops into Syria.

A source added: ‘The SRR is using strategic drones, which provide an overview of the ground, and tactical drones which can look over the walls of buildings and provide sharp pictures of suspects’ faces.

‘The ground inside Syria and Iraq is well known to British Special Forces after the previous Gulf wars. In 2008, the SAS destroyed the Al Qaeda-Iraq leadership and we’re confident we can do the same to IS.’

A Ministry of Defence spokesman said: ‘We do not comment on Special Forces operations.’

The SAS are using a range of high tech surveillance techniques on the hunt for 'Jihad John' and his friends

James's last letter... I'll be home for sister's wedding

By Caroline Graham

James Foley’s last loving message to his family was memorised by a fellow hostage, The Mail on Sunday has learned.

Danish photojournalist Daniel Rye Ottosen, 25, spent 13 months imprisoned alongside Foley and painstakingly committed to memory a lengthy final letter in which the American spoke hopefully about being freed in time to celebrate his sister’s wedding next year.

When Ottosen was released in June, his first call was to Foley’s mum Diane, when he dictated the lengthy letter to her.

His act of love and courage was revealed by the Foley family’s priest of 30 years, Father Marc Montminy, who said: ‘Jim was never allowed to send a letter like the other hostages because he was an American. Jim related the letter to the Danish hostage and he memorised it.

James Foley, pictured, vowed to a fellow hostage that he would make it home to his sister's wedding

‘Jim mentioned every family member and how much he loved them. He mentioned his mother, his father and his grandmother, who he was very close to.

‘He mentioned his brothers and his sisters and his nieces and nephews.

‘He said he loved them all and he knew they loved him and were praying for him and fighting for his release. He ended on a hopeful note by saying he’d be there for [Foley’s sister] Katie’s wedding.

‘She had just got engaged when he left for Syria so he must always have had hope he would come home.’

James’s mother Diane flew to Copenhagen the week before her son was executed to meet with Ottosen, according to the boss of the Boston-based online news organisation Foley was working for when he was snatched in November 2012.

Phil Balboni, CEO of GlobalPost, told how Diane developed a ‘close bond’ with the families of other hostages still in captivity and met up with released hostages from France and Spain who had been held by the same group of British jihadis dubbed The Beatles.

‘She went to Copenhagen to meet with the Danish journalist who memorised the letter. He provided new details of his time with Jim. All of the released hostages spoke of Jim’s courage. He was subjected to the most abuse and torture because he was American but they never broke his spirit.

‘Diane has become extremely close to the families of other Western hostages who are still in captivity. They share a special and very close bond.’

James Foley, pictured, was murdered by a masked ISIS terrorist with a British accent called 'Jihad John'

Balboni described Diane as ‘a woman on a mission’ to save her son from the moment the first email arrived from his captors on November 26, 2013.

‘The email was sent to me and to Jim’s brother Michael. It was brief. It said “We’re holding James. We’re prepared to negotiate for his release. We need money – FAST.”

‘They had all of Jim’s cellphone contacts which is how they got our email addresses.

‘There were more emails, five or six in all. They gave us the opportunity to ask proof-of-life questions, obscure family references impossible for anyone but Jim to answer. That was in early December, 2013. We felt great hope.’

In one email, the terrorists made their sole demand – for £80 million and the release of Muslim prisoners held by the US.

Balboni said the family had raised almost £3 million in ransom money. But then the terrorists stopped communicating.

After months of silence, the Foleys received a final email, dated August 12 – a hate-filled rant full of rudimentary spelling errors in which the jihadis vowed to execute Foley saying ‘You (America) and your citizens will pay the price of your bombings!

‘The first of which being the blood of the American citizen James Foley! He will be executed as a DIRECT result of your transgressions towards us!’

The email may have been written by ‘John’, the British jihadi who beheaded Foley, reports claim.