James Le Mesurier, British ex-army officer who trained Syria's White Helmets, found dead in Istanbul

Mystery surrounds the death of the former British soldier who backed Syria’s White Helmets after his body was found in the street days after the Kremlin accused him of being an MI6 agent with terrorist connections.

James Le Mesurier, an ex-Army officer, is thought to have fallen from the balcony of his home in Istanbul where he lived with his wife.

British intelligence agencies are monitoring the situation with Whitehall sources stressing it was too soon to say if Mr le Mesurier was a victim of foul play.

The intelligence services have warned against persistent Russian smears, of Mr le Mesurier over his support for the rescue group.

One Syrian expert said he had faced “unimaginable pressure and targeting as a result”.

Istanbul detectives are investigating his death and while the exact circumstances remain unclear, Turkish security officials suggested it was being treated as a suspected suicide.

Mayday Rescue, the organisation Mr Le Mesurier set up, confirmed he had died but warned against “unnecessary speculation about the cause of his death until the investigation is completed”.

Mayday Rescue organised and trained the White Helmets rescue group, which was set up in 2013.

It has since grown into a vast network of volunteers operating in opposition-held areas of Syria and scrambled to rescue civilians targeted in air raids conducted by the Assad regime and aided by the Syrian president’s Russian allies.

“James dedicated his life to helping civilians respond to emergencies in conflicts and natural disasters,” Mayday Rescue said in a statement. “[The White Helmets’] work has saved countless lives of civilians affected by the conflict.”

He was awarded an OBE in 2016 for his work to protect civilians in Syria and both he and the White Helmets received international media attention and were the subject of an Oscar-winning documentary.

But Mr Le Mesurier was the target of a disinformation campaign by the Kremlin, which accused him - sources insisted falsely - of being a British intelligence agent and even an al-Qaeda supporter.

As recently as three days ago, the Russian Ministry of Foreign Affairs had accused Mr Le Mesurier of being a ‘former agent of Britain’s MI6’ and working for the agency in the Balkans, Middle East and Kosovo.

In the Twitter posting, the Russian authorities added: “His connections to terrorist groups were reported back during his mission in Kosovo.”

Karen Pierce, the UK ambassador to the United Nations, said claims that Mr Le Mesurier was a spy were “categorically untrue” and she urged Turkey to carry out a thorough investigation of his death. She called him a “true hero” and humanitarian.

Turkish security sources said Mr le Mesurier had been found dead in the early hours of yesterday morning outside his home in central Istanbul’s Beyoglu district.

“He appeared to have fallen from a height. Current information suggests he had committed suicide,” the source told Middle East Eye news website.

A second Turkish source claimed his apartment could only be accessed using fingerprint identification.

“Mesurier and his wife appear to be alone in the building at the time of the death,” said the source.

A security source told Reuters news agency: “Le Mesurier’s wife told police that she and her husband had taken sleeping pills around 4am and went to bed.

“She said she was later woken by knocking on the door and discovered that her husband was lying on the street surrounded by police.”

The Turkish news-wire Demioren News Agency reported that police had found his face had been cut by a sharp object.

On Twitter, the White Helmets said in a statement: “We have learned with shock and sadness the news of the death of James Le Mesurier, founder and director of the humanitarian organization Mayday Rescue, early on Monday at his home in Tophane in Istanbul, Turkey. Mayday is one of the institutions supporting the White Helmets.”

Emma Beals, editor of the Syria In Context website, said: “James is one of only a few people in the world who took concrete action to save Syrian lives. He faced unimaginable pressure and targeting as a result.”

Hamish de Bretton-Gordon, a former Army officer who served with Mr Le Mesurier in the military and later worked with him on advising humanitarian NGOs in Syria, said he seemed in “good heart” when he met him in Istanbul last month.

He said Mr Le Mesurier knew he was the target of Russian-fuelled vitriol and took precautions.

“He took security seriously,” he said. “He was a soldier and he knew the risks of operating in this world and did all he could to minimise them.”

Mr Le Mesurier’s body was due to be handed over to the Forensic Medicine Institute for an autopsy before being repatriated to the UK.

“The Syrian civil defence family extends its deepest condolences to James’s family, and we express our deepest sorrow and solidarity,” the White Helmets said in a statement.

Mr Le Mesurier was born in Singapore into a military family. He graduated from Sandhurst and served with the Royal Green Jackets in Northern Ireland, Bosnia and Kosovo. He is understood to have married last year.

A Foreign Office spokesperson said: “We are deeply saddened by the news of the death of James Le Mesurier. Our condolences go out to his family and friends at this difficult time.”