Sas Rogue Heroes by Ben Macintyre
The Authorised Wartime History
In the summer of 1941, at the height of the war in the Western Desert, a bored and eccentric young officer, David Stirling, came up with a plan that was radical and entirely against the rules: a small undercover unit that would inflict mayhem behind enemy lines.
Despite intense opposition, Winston Churchill personally gave Stirling permission to recruit the toughest, brightest and most ruthless soldiers he could find. So began the most celebrated and mysterious military organization in the world: the SAS.