The Ministry of Defence has named one of the two soldiers who died during an exercise on Pen y Fan.
Lance Corporal Craig Roberts, 24, was taking part in selection trials for the SAS on south Wales’s highest mountain on Saturday, the hottest day of the year.
He and another Territorial Army soldier died and another is seriously ill in hospital.
An MoD spokesperson said: “It is with great sadness that the Ministry of Defence can confirm the death of LCpl Craig Roberts and another Army reserve soldier during a training exercise in the Brecon Beacons at the weekend.
“Our thoughts are with their families and friends at this difficult time.”
Lance Corporal Roberts was originally from Penrhyn Bay near Llandudno and taught at a school in London.
Pen y Fan, at 886m (2,907ft) the highest mountain in the Brecon Beacons, is the scene of the gruelling Fan Dance test, which sees soldiers take part in a gruelling timed double ascent and descent of the peak.