Although this is not related to our current discussion of The Waste Land, I discovered an article discussing the role of Girl Guides (or as we know them in America, Girl Scouts) as messengers for MI5 during WWI.  Their work was also mentioned in the British Secret Service's 100th Anniversary speech.

According to the article, these Girl Guides--who were between the ages of 14 and 16--acted as messengers, delivering highly classified information.  In some cases this information was so highly classified that it had to be delivered orally, showing a high level of trust.

Boy Scouts were originally included in this program.  However, they were removed from the program because "Girl Guides were more efficient because they were less boisterous and talkative."