Video report by ITV News International Affairs Editor Rageh Omar
A former British army officer who helped found the White Helmets volunteer organisation in Syria has been found dead in Istanbul.
James Le Mesurier was discovered on the street below his apartment in the early hours of Monday.
Le Mesurier, who died aged 48, was born in Singapore in 1971, the son of Benjamin Havilland Churchill Le Mesurier.
Before founding the White Helmets, also known as the Syrian Defence League, Le Mesurier was a member of the British Army, having trained at the Royal Military Academy at Sandhurst and would go on to receive the Queen's Medal.
Le Mesurier moved through the ranks to become an Officer and worked with with the United Nations peacekeeping force in the former Yugoslavia.
During his time in the army he carried out tours in numerous countries including Iraq and Ireland.
In 2013 he set up Mayday Rescue who trained the White Helmets, who go into bombed areas in war-torn countries to assist civilians.
The organisation claim they have rescued more than 100,000 people during the Syrian War.
The group say 252 volunteers have died since their formation, with the Syrian government treating them as a terrorist organisation.
In a statement, the organisation confirmed Mr Le Mesurier's death and paid tribute to the "visionary" and "dear friend".
"James dedicated his life to helping civilians respond to emergencies in conflicts and natural disasters," Mayday said.
"Nowhere was the impact of his important work felt so strongly as in Syria, where Mayday supports a network of volunteer rescue workers known as Syria Civil Defence, also known as The White Helmets.
"Their work has saved countless lives of civilians affected by the conflict.
We ask that James’s family, friends and colleagues be given time, space and privacy to grieve this terrible loss...
"We ask that James be remembered as what he was: a great leader, a visionary, and a dear colleague and friend."
In 2016, Le Mesurier received an OBE for "services to the Syria Civil Defence group and the protection of civilians in Syria".
During the same year the Syrian Defence League was nominated for the Nobel Peace Prize.
The White Helmets were also the subject on a Netflix documentary which won an Academy Award three years ago.
Le Mesurier was accused of being a former MI6 spy as recently as Friday by the Russian Ministry of Foreign Affairs, who tweeted: "The White Helmets' co-founder, James Le Mesurier, is a former agent of Britain's MI6, who has been spotted all around the world, including in the Balkans and the Middle East.
"His connections to terrorist groups were reported back during his mission in Kosovo."
He had lived in Turkey for the last four years with his wife.