During the Second World War members of the RAF Police started wearing woollen armbands whilst on duty to show their role and authority to police members of the RAF. The armband has remained externally unaltered through to the present day, although the original method of securing it with press studs has now been superseded. Originally the armband was used on duty, although today it is an element of the dress uniform:
The armband made of dark blue flet, with a red central band and the initials ‘RAFP’ embroidered in the centre:
The modern version of the armband secures with a pair of Velcro strips:
The interior of the armband has a pair of stickers that give care instructions and the NSN numbers:
Note also the brass hook at the top of the armband used to prevent the armband from slipping down the arm.
The 2004 RAF dress regulations give the following instructions on the armlets wear:
a. Armlets. The RAFP armlet is to be worn on the left arm, above the elbow, when in No 1 SD and No 6 SD (Jacket). It is also provided for wear on those protective outer garments that are not fitted with shoulder straps. The DPM/PM and AO FP armlet may also be worn by entitled officers holding these appointments.
Tales from the Supply Depot 
Doesn’t seem to sit all that straight on the arm, but the rest of the young Cpl’s uniform isn’t sitting much better, the SWO would have used him as a ‘training aid’ on dress 😉
The chain going into the top pocket is interesting, I wore something similar in uniform with a whistle attached, an old tradition going back many years that could still prove useful even in the day of radios and ‘panic buttons’, it was on a braided lanyard when in dress uniform but we had epaulets and rank boards so that was a better option and something to make civilians ask questions 🙂