What British Army regulation was abolished on 6 October 1916?

Unlike the Royal Navy, which has always allowed beards, the British Army has been rather ambivalent about facial hair.

Until the mid-19th century, facial hair was unusual in the Army, except for the infantry pioneers, who traditionally grew beards. A small minority of officers wore moustaches.

During the 1800s, the attitude to facial hair changed as a result of the Indian and other Asian Wars. Many Middle Eastern and Indian cultures associated facial hair with wisdom and power. As a result, facial hair, moustaches and side whiskers in particular, became increasingly common on British soldiers stationed in Asia. In the mid-19th century, during the Crimean War, all ranks were encouraged to grow large moustaches, and full beards during winter.

After the Crimean war, regulations were introduced that forbade serving soldiers of all ranks from shaving above their top lip, in effect making moustaches compulsory for those who could grow them, although beards were later forbidden.

The moustache regulation remained in place until the middle of World War I, when it was abruptly abolished by an Army Order dated 6 October 1916. The order was issued by Lieutenant-General Sir Nevil Macready, Adjutant-General to the Forces, who loathed his own moustache and immediately shaved it off. However, there is evidence in photographs and film footage that the previous regulation was widely ignored and that many British soldiers of all ranks were clean-shaven even before 1916.