A senior special forces officer has told an inquest that a risk assessment conducted during an SAS test march was "not sufficiently good" enough to prevent the deaths of three reservists.
Soldier AA, an assistant chief of staff overseeing members of the Army reserve, also said he had been unable to fully investigate the deaths because of a criminal inquiry.
Lance corporals Edward Maher and Craig Roberts, and Corporal James Dunsby, all died after collapsing due to heat stress on the Brecon Beacons in South Wales on July 13 2013.
Giving evidence anonymously to the fourth week of an inquest into all three deaths, officer AA claimed a generic risk assessment prepared before the march had been acceptable.
But he conceded that there had been a "serious error" on the day of the march and that the dynamic assessment of soldiers' safety conducted by commanders on July 13 had failed.
Speaking from a specially-constructed witness box shielding him from view, AA said of some march directing staff: "We organisationally have failed to give them either the knowledge or the understanding (of heat illness) that was required.
"The most likely cause of the people planning and executing the exercise not knowing the full provisions (of MoD heat illness guidance) is that their understanding had relied very much on self-learning or the courses that they had previously run, and experience that they gained on them."
Officer AA added: "The dynamic risk assessment that happened on the day failed and was not sufficiently good to prevent these three young men dying."
It also emerged during AA's evidence that test marches were not "recommenced" until a Health and Safety Executive improvement notice served on the MoD in October 2014 had been complied with.
Describing contact with the HSE as extremely helpful, AA told the inquest: "We take the safety of our soldiers very seriously.
"We try very hard to make the environment as safe as possible for our students to operate within.
"We are immensely grateful to those who have been able to investigate and point out our shortcomings."
Action had since been taken to make the system safer for special forces candidates, AA said, including extensive training to ensure compliance with the HSE improvement notice.