An SAS training officer has told an inquest into the deaths of three reservists that he did not adhere to MoD guidelines on heat stress.
Soldier 9F also claimed that stopping selection tests in the face of heat casualties, as stipulated in MoD documents, was "not an option" given the intensity of special forces training.
During his testimony to an inquest in Solihull, West Midlands, the training officer was accused at one point in his evidence of having a "Darwinian approach" to the fatal test march.
The inquest has heard that Signals Regiment directing staff oversaw the exercise on which lance corporals Edward Maher and Craig Roberts collapsed and died.
Corporal James Dunsby died in hospital after falling victim to heatstroke in the final stages of the 16-mile route on the Brecon Beacons on July 13 2013.
9F, who had trained regular unit soldiers taking part in the selection exercise, became aware in the late afternoon that there was a incident involving reservists and that Signals unit directing staff had requested medical support.
But he only found out at 8pm that there had been fatalities on the reservists' "test week" march.
Invited by Birmingham Coroner Louise Hunt to give his view of a heat stress chart in an MoD force protection and treatment document dealing with climatic injury, 9F said: "We could not do what we do if we adhered to those guidelines.
"It would significantly inhibit the type of training and the selection that we are trying to achieve.
"Stopping the training because it reached a certain heat stress was not an option for me."
Referring to the official heat illness document as a "pamphlet", 9F added that members of his unit were required to deploy anywhere in the world at 24 hours' notice and work in conditions where acclimatisation was "limited if not non-existent".
The training officer said more medics had been posted to deal with a regular unit march than had been deployed on that undertaken by reservists.
"It's incumbent upon us to make sure that we provide the safest and best environment we can within the context of what we need to achieve," he told the 15th day of the inquest.
But he said he believed he was able to diverge from the MoD guidelines "because guidance implies that it is only guidance".
After being asked how important personal administration was to heat illness, 9F added: "It's fundamental that the individuals take a responsibility for this themselves.
"This is not routine training, this is a voluntary course that they spend years preparing themselves for mentally and physically.
"The next phase we take the students on is to the jungle."
David Turner QC, representing the widow of Corporal Dunsby, put a series of questions to 9F after asserting that his evidence seemed "to suggest a Darwinian approach to this exercise".
Mr Turner asked 9F: "In relation to test week, are you looking for personnel who will take themselves beyond the limits of where they have been before?"
9F answered: "One of the primary things we are looking for in our students is maturity of judgment. I think all of them by their very nature want to be special and want to be the best they can be."
Questions about possible heat-related casualties experienced by candidates for the lead regular unit on July 13 and in prior marches were put to 9F, who gave evidence from inside a screened-off witness box.
The training officer said he had looked into what were believed to be heat illnesses and came to the conclusion that individuals were "not doing what they should have been doing" with regards to hydration.
One regular soldier who complained of potentially heat-related symptoms turned out to have been taking strong pain-killers for a knee injury, 9F told the coroner.
Explaining how another candidate had undertaken a march after failing to realise he had malaria, 9F said: "One of the students reported sick in the evening.
"His temperature was above normal and he was mildly feverish. The doctor said he wanted to withdraw him because he was suffering the signs of heat illness.
"I didn't believe that he had heat illness because he was one of my fast runners.
"It turned out subsequently that he had been on holiday in the Far East and was suffering from a mild form of malaria, so it wasn't heat."
The inquest was adjourned until Monday.