"It was this kind of mental toughness [to walk for five days on suppurating flesh which had in places decayed to the bone] which the SAS was constantly looking for in the screening tests. Such qualities were not, of course, only to be found in the SAS but they were more in demand there than anywhere else. The order of priorities was intelligence, mental toughness, physical toughness. Without intelligence the other two qualities would not enable a man to survive and be useful, without mental toughness he would never reach the peak of his performance."

"The aim of the selection course is to find a man who has initiative, self-discipline, independence of mind, stamina, patience, a sense of humour, and the ability to work without supervision. These are all desirable military qualities in any unit. In addition to these he must be the sort of person who can endure loneliness - in complete isolation or in a very small group - without deteriorating. Some men are good on their own but lose initiative in a small group and pull less than their weight. He should be neither a complete 'loner' nor yet a man who needs at least a platoon to give him moral support. The qualities which are looked for tend to be care in recording information, ability to recall the exact sequence of events, a logical mind, and the presence to keep himself in trim physically no matter how exhausted he may become."