An infantry soldier died during a training exercise in Wales's mountainous Brecon Beacons area on Tuesday, the hottest day of the year.
The Ministry of Defence (MoD) on Wednesday confirmed the death of the soldier, who was from the Rifles regiment. Three soldiers died in the same region during a gruelling Special Air Service (SAS) cross-country selection test on one of the hottest days of 2013.
Earlier this year, British health and safety officials said they would give the MoD a "Crown Censure" over those deaths. A coroner overseeing an inquest into the deaths last year said there had been a catalogue of mistakes, the risk assessment for the march had not been adequate and the response to the incident had been chaotic.
Temperatures in Britain on Tuesday were the hottest of the year so far, the Met Office said, reaching above 30C in many places. The highest July reading ever recorded in the UK was 36.7C (98F) last year. The hottest temperature ever recorded in Britain was 38.5C (101.3F) in Faversham, Kent, in August 2003.