An infantry soldier has died while on a training exercise in the Brecon area of Wales.
The soldier, from The Rifles regiment, died on Tuesday - Britain's hottest day of the year so far.
Temperatures on Tuesday peaked at just above 30C (86F) in Brecon, the Met Office said.
Following Tuesday's death, an Army spokeswoman said: "We can confirm that a soldier from ITC Catterick died on 19 July while conducting pre-course training for the Platoon Sergeants' Battle Course in Brecon."
This has happened before - back in 2013, three soldiers died during an SAS training exercise in the Brecon Beacons on one of the year's hottest days.
Lance Corporals Edward Maher and Craig Roberts were pronounced dead on the Brecon Beacons after suffering heatstroke during a 16-mile (26km) SAS test march.
Corporal James Dunsby died from multiple organ failure in Birmingham's Queen Elizabeth Hospital more than two weeks later.
A coroner ruled that neglect played a part in their deaths.
In March the Health and Safety Executive announced it would issue a so-called Crown Censure to the Ministry of Defence over the 2013 deaths.
It said the MoD had failed to manage risks during the training exercise and added that it had worked since the deaths to ensure lessons were learned and future risks reduced.