One of two servicemen who died during a military training exercise believed to be part of selection for the Territorial Army’s SAS is named as Lance Corporal Craig Roberts.
Sources said the men had completed a period of training and preparation but were at the beginning of the assessment phase of the process.
Police and the Ministry of Defence (MoD) are continuing to investigate their deaths, while a third serviceman remains in a serious condition in hospital.
The MoD was not expected to name the second soldier.
The trio were part of a group training on Saturday when the mercury hit 29.5C (85.1F).
Soaring temperatures may have been to blame for their deaths, military sources said, and it is understood live ammunition was not involved in the incident.
It is believed they were members of the TA aspiring to join the reservists’ branch of the SAS, although the MoD has not yet given official confirmation.
In a statement, the MoD said: “It is with great sadness that the Ministry of Defence can confirm the death of L/Cpl Craig Roberts and another Army reserve soldier during a training exercise in the Brecon Beacons at the weekend.
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“Our thoughts are with their families and friends at this difficult time.
“The families of the soldiers have requested that their privacy is respected at this difficult time.”
The Brecon Beacons in Wales is one of several locations British military use as part of their training. Its rugged and sprawling terrain is considered an ideal area for elite forces personnel like the SAS, by helping to prepare soldiers physically and mentally for warfare as well as put their logistic skills to the test.
Earlier this year an army captain was found dead on a snow-covered Corn Du mountain. It was thought that Rob Carnegie had been taking part in a gruelling 17 to 40 mile march in freezing conditions in the Brecon Beacons as part of a selection process for the special forces regiment, when he collapsed and died.
News of the deaths has been met with shock in the nearby town of Brecon, which is home to The Infantry Battle School.
Brecon mayor and Powys county councillor Matthew Dorrance said: “It’s incredibly sad for the friends and family of the people who have lost their lives and our thoughts are with the person who is injured.
“In one way we’ve been blessed with the weather but for people working in this heat, they’re tough conditions.”
Mr Dorrance added that locals regularly saw troops training in the area. “We’re proud of our links with the military in the town,” he said.
A Dyfed Powys Police spokesman said: “The Ministry of Defence are fully co-operating with our inquiries.
“The next of kin and HM coroner have both been informed.”
Major Alan Davies, who was involved in contingency planning during the first Gulf War, told the BBC that the Beacons is one the most challenging terrains military personnel can encounter.
“On one end of the spectrum you have cadets being taken for mountain walking and at the other end of the spectrum the SAS use it,” he said.
He added that the three men may have been carrying very heavy equipment and working to a deadline, which meant they would have been pushing themselves very hard.
News of the deaths was met with shock in the nearby town of Brecon, which is home to The Infantry Battle School.
Brecon Mayor and Powys county councillor Matthew Dorrance said: “It’s incredibly sad for the friends and family of the people who have lost their lives and our thoughts are with the person who is injured.
“In one way we’ve been blessed with the weather but for people working in this heat, they’re tough conditions.”
Members of all four of South Wales’s mountain rescue teams were called out to assist when the two servicemen died.
Thirty members of Central Beacons, Brecon, Western Beacons and Abergavenny-based Longtown Mountain Rescue Teams joined the operation near Pen y Fan, which is the highest mountain in South Wales.