I think Stephen Ambrose wrote about that training program in one of his books, too.
Am I mistaken, or is the caption to the picture of our Rangers setting off on a 20-mile hike incorrect? I don't think they're wearing British uniforms, but rather, they're wearing the US Army field uniform current in June 1942, with the tin hat (the old Brodie/Kelly helmet). The M1 helmet was introduced at the end of 1941, if I remember correctly, but hadn't completely replaced the old helmet at that time. At least, the Navy and the Marines still had the old helmets. But I may be mistaken.
Prost!
Brad