TIL that during WW1, the MI5 used Girl Guides to deliver secret messages. They used Girl Guides instead of Boy Scouts because they found out that Boy Scouts weren't efficient enough, boisterous and talkative.

Working for MI5 is probably the last thing you would expect of a Girl Guide, but a top- secret document has revealed that 90 teenage Guides worked for security service MI5 in the First World War. It explains their working conditions, responsibilities, qualifications and pay scales.

All the girls who worked for MI5 between 1914 and 1918 were aged from 14 to 16. Their main role was as 50p- a- week messengers distributing highly classified information. The teenagers were so trusted by MI5 that they were allowed to relay some of the messages verbally. At the start of the war Boy Scouts were also used. But it quickly became clear that Girl Guides were more efficient because they were less boisterous and talkative.

The role of the girls was uncovered when Girlguiding UK and MI5 researched their histories as part of their centenary celebrations. MI5, which was founded in 1909, tracked down a secret document called Duties of H Branch, which specifically covered the role of the Girl Guides. They worked at Waterloo House and two other offices in central London, where they were divided up into five or six Guides under a patrol leader. Section H5 in the document states: "Each is allotted to a floor and the patrol leader is responsible for the work, discipline and good behaviour of her patrol.

"The Guides are allotted marks each day by their patrol leaders and at the end of the month the room which has proved most generally satisfactory is awarded the prize picture for the following month."

Section H6 adds, "A messenger should be between the ages of 14 and 16, a Guide of good standing, quick, cheerful and willing. Guides are engaged on three months' probation. The initial rate of pay is ten shillings a week (50p) with dinner and tea included. Guides who do special work, or who have special responsibilities, receive a higher rate of pay. Those who help in the kitchen receive four shillings and sixpence (22½p) extra duty pay per month. The guides are paid weekly by the Captain on Friday morning. The hours of work are from 9am to 6pm and 10am to 7pm on alternate weeks. Fifty minutes are allowed them for dinner and 20 minutes for tea. Girl Guides are on duty on alternate Sundays and they get one half- day off duty each week. A week's holiday is given in the summer and short leave at Christmas and Easter. When a Guide falls sick, a doctor's certificate must be sent within 48 hours of the illness. Otherwise, all pay is stopped."

The document also explains the duties of the Guides. It says, "The Guides are responsible for dusting all rooms on their floors between 9am and 10am, cleaning and filling the ink pots and disinfecting the telephones, as well as answering any bells which may ring between those hours. After 10am their work consists chiefly of collections for the despatch room, for the posts, and for running messages, sorting cards, collecting files, collecting waste paper and rolling it up ready for burning."

The Girl Guides were formed by Robert Baden- Powell in 1910. The movement was considered radical at first. In an age when skirts were ankle length and young ladies never ran, the idea of girls camping, hiking and the like did not go down well.

Critics denounced "girl scouting" as a "mischievous new development", a "foolish and pernicious movement" and an "idiotic sport". But, determined to show they could beat the boys at their own game, these fledgling Guides threw themselves into the new movement. By 1912 badges on offer included air mechanic, cyclist, electrician, sailor, telegraph operator and even tailor. They were 300,000- strong by the start of the First World War.

Government departments began contacting the Girl Guides and the Boy Scouts, seeking teenagers to work as messengers and backroom staff to assist the war effort. At first there were both Scouts and Guides working for MI5. But it soon became clear that the boys were too boisterous and talkative and couldn't adapt to periods of inactivity between their duties. It was felt that the girls were more restrained and could be trusted to a greater degree, so the Boy Scouts were phased out. A total of 90 Guides worked for MI5 during the course of the war and their main duties were as messengers, which often involved them going out of the buildings. Some of the top- secret messages had to be passed on verbally, which shows how much the girls were trusted.

The Guides had to observe a strict dress code which laid down that their blue skirts must be no more than eight inches off the ground. They had to wear a belt and their distinctive hats at all times. Praising the work of the girls, Baden- Powell once said: "One of the big government offices in London has taken on Girl Guides as confidential messengers and orderlies - avowedly because 'they can be trusted, better than boys, not to talk'. If the character of the girl is developed, she will discipline herself not to 'blab' and will 'play the game' not for herself and her own glorification - but in the interests of her side, that is of her country or her employer."

In a modern link, Dame Stella Rimington, MI5's first woman director general and the first to be officially identified, was a Girl Guide.