A British Army reservist who died while attempting to join the SAS had a body temperature of 41C on the day he collapsed during a selection march.
Corporal James Dunsby was one of three men who died following the 2013 exercise in the Brecon Beacons.
Despite data from a nearby weather station showing that the temperature in the mountains reached 27C there was no additional water available for the candidates at checkpoints.
Paramedic Damon Jones is among those giving evidence at the inquest into the deaths. In a letter he explained how when he reached him Corporal Dunsby was "boiling to touch, but going pale. His body was shutting down.
Adding that it was the highest temperature he'd seen in 23 years as a paramedic Mr Jones said "His eyes were glazed over like fish eyes. In the ambulance he was rigid and showing signs of brain malfunction. I didn't think he'd survive."
James Dunsby died two weeks later in hospital from organ failure brought on by hyperthermia.
The inquest into his death and those of Lance Corporal Craig Roberts and Trooper Edward Maher is continuing in Solihull.
Army personnel, their identities protected and evidence given behind screens, have also given evidence - describing in graphic detail how Trooper Edward Maher was found.
A soldier known only as 1N was sent to find him after his tracking beacon showed no movement. Upon reaching him, two and a half hours since the last 'active ping', Maher was found sitting up with a half eaten chocolate bar in his hand and a bottle of water.
1N said Trooper Maher " literally looked like he'd stop to take a five minute break" but "showed no indication he was alive"
He then called for immediate evacuation as he began CPR on Maher despite him being "cold to touch" and his jaw "locked up".