The father of a reservist who died following an SAS test march was taken to the wrong location after asking to see where his son collapsed, a coroner has heard.

An inquest into the death of Corporal James Dunsby heard there was ''no rhyme or reason'' as to why David Dunsby was taken to the wrong grid reference on the Brecon Beacons.

The error was revealed by Mr Dunsby's barrister, Keith Morton QC, during questioning of an SAS training officer who co-coordinated the fatal march on July 13, 2013.

Cpl Dunsby, from Trowbridge in Wiltshire, died in hospital 17 days after the test march and two other reservists were pronounced dead on the hills.

The inquest has heard that Cpl Dunsby and Lance Corporals Edward Maher and Craig Roberts all suffered fatal heatstroke as temperatures nearby peaked at 28.1°C (82°F).

During his questioning of a training officer known by the codename 1B, Mr Morton pointed out that a previous witness, Soldier 1J, had indicated that he was sent to a different area near where Cpl Dunsby was discovered.

Mr Morton then said to 1B: ''After the event, Mr Dunsby, James's father, was taken to a location which he was told was the point where James was found.

''That too was in the area (previously indicated by 1J) which is obviously wrong.''

Soldier 1B, a Royal Marine who joined the special forces in 1993, answered: ''There is no rhyme or reason why that should have been done.

''There is a 10-figure grid reference as to where James was found. The guy from my location got to him.''

1B, who recently left the military after 29 years' service, was giving evidence for a second day to the inquest in Solihull, West Midlands.

Asked about his risk assessment for the march and his actions on July 13, 1B said more than 70 SAS candidates, including the men who died, were making good time before a ''catastrophic'' situation developed.

Soldier 1B told the hearing: ''I had 78 runners on that route.

''Six people had been withdrawn. The other 72 runners that were going around, apart from 1W, were completing that march within the allotted time and that includes Ed and that includes Craig and that includes James.

''The two heat casualties - within 20 to 30 minutes their vital signs had recovered.

''None of the qualified medics there told me that they needed further assistance and they were waiting to be taken back to camp.

''Students were making good time. In fact I thought that they were doing well on that march.''