Dr Michael Mosley is believed to have died of heat exhaustion after losing consciousness while walking in 40C temperatures, Greek police say.
An initial examination, based on CCTV footage and forensic evidence, suggests he died of natural causes, The Telegraph understands.
Police have ruled out foul play or criminality, according to sources.
Officers are also investigating CCTV footage that appears to show Dr Mosley disappearing from view as he makes his way down a hillside, close to where his body was later found on the island of Symi.
Dimos Kotsidaras, police commander for Symi, said it was believed “the cause of death was heat exhaustion after walking from St Nikolos to Agia Marina in high temperatures”.
Dr Mosley sat down before losing consciousness in the 40-degree heat only yards away from safety, interim findings from a coroner found.
The inquiry into his death, based on CCTV footage and forensic evidence, suggests he died of natural causes, The Telegraph understands.
Greek police have ruled out any possibility of foul play or criminality, according to sources.
Police are also investigating footage that appears to show Dr Mosley disappearing from view as he makes his way down a hillside close to where his body was later found.
The area where Dr Mosley was discovered is one of the hottest in the region and the local temperature between Wednesday and Sunday reached north of 40C.
Dr Mosley was found lying on his back, suggesting he had tried to raise his leg upwards, suggesting he had tried to stop himself fainting, police sources disclosed.
The details came as Rishi Sunak joined close friends in paying tribute to Dr Mosley
Downing Street said he was an “extraordinary broadcaster” who had a “huge impact” on people’s lives.
The Prime Minister’s official spokesman said: “The reports from the weekend are heartbreaking and our thoughts are with Dr Michael Mosley’s family, his wife Clare and friends, in what must be deeply sad times.
“We have seen some incredibly touching tributes which have made clear the huge impact that Dr Mosley had on people and helped to transform people’s lives for the better.
“He will be known as an extraordinary broadcaster who used his platform to influence and change the way we think about many public health issues.”
Meanwhile, three close friends of Dr Mosley laid a single flower on the mountainside where he was found.
A woman and two men sailed on a small private boat on Monday morning to the beach resort of Agia Marina.
Dr Mosley was found 50 yards away from the resort on Sunday morning, five days after his wife reported him missing.
The group were seen tentatively making their way over the rocks towards the site where Dr Mosley was discovered by a bar manager.
Visibly distressed, the group laid a single-stemmed white and pink Oleander and were seen hugging and consoling each other for around 20 minutes.
One of the party was a young male British volunteer who had helped search the island for Dr Mosley.
The Oleander has poetic significance in Greek mythology. According to one legend, Hero, a priestess of Aphrodite, is wooed by a young man called Leander, who swims across the Hellespont every night to see her.
One night during a violent storm he is dashed against sharp rocks and washes up on the beach.
Dr Mosley’s body lay undiscovered just yards from a beach resort, as his wife said he “so very nearly made it” to safety.
CCTV footage shows Dr Mosley gingerly walking down a rocky mountain near the perimeter fence of the Agia Marina resort before he appears to stumble and fall out of view, just over two hours after he left his wife and friends.
His wife, Dr Clare Bailey Mosley, paid tribute to her “wonderful, funny, kind and brilliant husband”.
She said: “We’re taking comfort in the fact that he so very nearly made it. He did an incredible climb, took the wrong route and collapsed where he couldn’t be easily seen by the extensive search team.”
Volunteers on Symi said “high temperatures” and “rough spots” made the search for Dr Mosley “particularly difficult”.
The Symi Crisis Rescue Volunteer Team posted a tribute to Dr Mosley’s family on their official social media page.
A spokesman said: “We would like to extend our deepest condolences to Dr Michael Mosley’s wife, children, relatives and friends for his tragic loss.
“Our team was called in by island authorities to assist in the search investigation on the very first night of his disappearance and we immediately began with a first night search.
“We continued all the coming days to participate in the investigations together with firefighters, police officers and other volunteers, as always directed by the head of the investigation.
“High temperatures and rough spots made this mission particularly difficult, and unfortunately, the outcome was one we all know.”
