The Royal Army, as well as the armies of some commonwealth nations, has a peculiar rank in its structure that allows the soldier to wear a full beard and apron and carry a large ax while on parade: the pioneer sergeant.
Pioneer sergeants, as they are known, date back to the 1700s when the men selected for this duty were expected to act as a unit blacksmith as well as a sort of early combat engineer, cutting the way through forests and other obstacles to allow other troops to move behind them with additional equipment and arms. They also had ... other duties.
One of the grislier duties of this particular rank was to cut the legs off of dead horses after they fell, whether in combat or due to some other injury or illness. The horses had one branded leg that would identify them. Collecting it prevented soldiers from selling their horse and claiming it had died to get a free replacement.
And while the apron would certainly have come in handy during that duty, it also served as protective gear when the pioneer sergeant was working at a forge. The beard worked with the apron to protect the soldier from the heat and slag.
The Australian Army officially adopted the beard for pioneer sergeants in 1965 when a governor general suggested it for the 4th Battalion, Royal Australian Regiment. The 2nd Battalion, Royal Australian Regiment, pioneer sergeant was officially authorized a beard in 2007. As of 2009, only the 2nd Bn. was actually taking part in the tradition, as the 4th Bn. had re-flagged as a commando unit and had no pioneer sergeants.