Video report by ITV News Correspondent Ivor Bennett
The family of a British climber who died on the slopes of Mount Everest has paid tribute to the "aspirational adventurer."
His partner, Kristyn Carriere, who was at the base camp, said on Facebook: "He got his goal. My heart is broken. It was his ultimate challenge."
The Foreign Office is aware of reports but has not yet been formally informed of any incident.
Robin's family has since paid tribute to the climber who "lived life to the full".
In a statement they said: "He achieved so much in his short life, climbing Mont Blanc, Aconcagua and Everest.
"He was a “tough guy”, triathlete, and marathoner. A champion for vegetarianism, published author, and a cultured theatre-goer, lover of Shakespeare.
"We are deeply saddened by his loss as he still had so many more adventures and dreams to fulfil.
"Everyone who ever met him in any capacity will always remember the positive impact he had on their lives.
"Robin is a much loved and loving son, brother, partner, uncle, and friend."
Murari Sharma, of the Everest Parivar Treks company that arranged Mr Fisher's logistics, confirmed he was 150 metres below the summit when he suddenly fell down.
A sherpa tried to wake him up, change his oxygen bottle and tried to give him some water but there was no response.
"Jangbu and other sherpas tried for a long time to wake Mr Fisher up but they couldn't," Mr Sharma said.
"He was a great man and a good friend and all of us are very sad.
"Our deepest condolences to Mr Fisher's family, friends, and colleagues for their loss."
Robin's death is just one day after the death of an Irish climber in the early hours of Friday.
Kevin Hynes, 56, died in his tent at 7,000 metres after turning back before reaching the summit.
The father of two was part of a group from UK-based climbing company 360 Expeditions which was attempting to scale the world's highest mountain.
It's known at least six people have died in the past week on Everest, with some reports suggesting the death toll has reached double figures.
His death comes a week after Trinity College professor Seamus (Shay) Lawless, aged 39 and from Bray, Co Wicklow, fell during his descent from the peak having achieved a lifetime ambition of reaching the summit.
The search for Mr Lawless has been called off.
An American climber, Austrian climber and two Indian climbers are also reported to have died in the last week.
The image, by climber Nirmal Purja, shows a huge human traffic jam on the mountain. The queues are making the descent riskier.