A military investigation into the deaths of three reservists in the Brecon Beacons has recommended more than 100 changes to ensure it never happens again.
A Service Inquiry by the MoD supported a coroner's inquest and found that LCpl Edward Maher, LCpl Craig Roberts and Cpl James Dunsby were not trained to the required standards.
The men died from heat exhaustion on one of the hottest days in 2013. They collapsed on a 16-mile SAS selection march, while carrying heavy packs and rifles.
The report found that there were significant failings in the preparation for the exercise.
It stated that the three suffered "exertional heat illness due to having had less experience and being less well prepared."
It contains a total of 114 recommendations, mainly focused on improving the safety and management of training systems.
The report also highlights that the organisers of the exercise, the Signals, didn’t reduce the risks as much as possible because they didn't fully understand what it entailed.
However, the MoD said that "substantial changes to the training and selection of specialist military reserve units" have been made since 2013.
These include a review of training locations, improved monitoring of candidates and an external watchdog for all training.
A spokesperson said: “With all the recommendations from this report having been or being addressed, we are committed to doing all we can to ensure such a tragic event cannot happen again.”
In 2015, a coroner said they died of neglect, and the Army accepted it didn't manage the risks of the exercise carefully enough.