Back in July 2015, a senior coroner, Louise Hunt, concluded that a “catalogue of very serious mistakes” had been made by many people involved in the planning and execution of an SAS test march in which three candidates had suffered fatal heat illness on a hot summer day.

Outside court, the Ministry of Defence claimed it had already made changes following the tragedy in the Brecon Beacons in 2013 and would do everything it could to prevent such a disaster happening again.

But on 19 July 2016 – almost exactly a year after the coroner’s highly critical remarks – there was yet another death in the same area of south Wales on a similar searingly hot day.

Carrying 25kg (55lb) of equipment, Cpl Joshua Hoole, 26, collapsed 400 metres from the end of an eight-mile course as the temperature built towards 30C (86F).

During the four-week inquest into Hoole’s death heard by the same coroner in Birmingham this October, many of the issues that were pored over during the SAS hearing came to the forefront again. How was the exercise planned? Should it have been stopped when soldiers began to fall? Did the army really understand the danger heat poses during training even in southern Britain? Had lessons really been learned since the SAS deaths?

Hoole was a talented and popular member of 1 Rifles from southern Scotland who joined the army in 2008, served in Afghanistan and had a bright future ahead of him. “He shone his light on all of us,” said his father, Phillip Hoole, himself a former army sergeant major. “Had his life not been extinguished, I am sure that he would have achieved much more.”

At first, it seemed that hot weather was not to blame. A defence service inquiry concluded Hoole had died not because of the heat but an undiagnosed underlying medical condition, sudden arrhythmic death syndrome.

But Hoole’s father came to doubt that conclusion and, believing there to be organisational failings in the way the exercise was handled, successfully applied for a full and detailed inquest to take place.

Phillip Hoole, Cpl Joshua Hoole’s father. Photograph: Jacob King/PA

During the inquest it has emerged that of the 41 corporals and lance corporals taking part in the annual fitness test (AFT) that day, only 24 completed the course. The average drop-out on the same route for the whole of the previous year was 3%.

Vivid accounts were given of how some of those who took part in the AFT came to fall.

Cpl Anasa Matau described being hit by “heat and exhaustion”. He said: “My core body was hot, I had salty deposits around my mouth and hands, and I told myself I thought I was dehydrated.” He was so confused that he tried to get his combat shirt off without removing his daysack. He was taken to hospital and was told he would have died if he had not stopped, the inquest heard.

The AFT in which Hoole died had been due to begin at 11am but started at 7am because hot weather was forecast. The inquest heard it was believed the temperature at this time was above 20C – the mark at which such exercises should not take place.

Prof George Havenith, a heat stress and heat strain expert from Loughborough University, was asked on a balance of probabilities whether the march should have gone ahead. Havenith said it should not. Asked if Hoole would be alive if the exercise had not been run or had been stopped half an hour before he collapsed, Havenith replied: “Yes.”

Havenith’s testimony echoed some of what he said during the SAS inquest. He argued then that inadequate planning for the treatment of casualties had contributed to the deaths in 2013 of Cpl James Dunsby, L/Cpl Craig Roberts and L/Cpl Edward Maher and said they would have survived if they had been stopped at the last checkpoint they had passed through.

As during the SAS inquest there was much focus on a piece of kit called the wet bulb globe thermometer (WBGT), which takes factors such as heat, humidity and wind into account when producing a reading.

Havenith told the inquest the readings from the WBGT could not have been relied on by those in charge of the exercise because it was positioned in the shade of a gym building.

The fitness instructors who were in charge of the WBGT on the day of Hoole’s death said they had not received any training on how to use the device for at least 10 years.

Despite the MoD’s promises to learn lessons after the SAS tragedy, worrying signs emerged that there may still be problems over the running of exercises on hot days.

A captain who signed off a risk assessment for the AFT said he had read a crucial document called JSP 539 – which relates to climatic illness and was featured repeatedly during the SAS inquest – but was not trained to interpret it.

The MoD has been keen to play down any link between the deaths of the SAS candidates and Hoole. The army cardiologist Maj Andrew Cox told the inquest he did not believe heat should be recorded as a factor in Hoole’s official cause of death. He suggested “exertion” could have been a contributing factor but said: “I believe this was a sudden arrhythmic death syndrome death.”

Hoole’s father, who had helped run similar exercises during his career, agreed that a number of factors could be at play but told the major starkly during the inquest: “I used to call it cooking yourself from the inside out.”