If we think RAF numbering is difficult, the army changed their sysytem for a "new" one seven times between 1810 [demi-official] and now.
1829, 1856, 1873, 1881, 1920, 1942, 2007 [JPA]
The changes were sufficient and sufficiently often to allow, with ease, several soldiers in the same regiment to have identical numbers. Rather defeated the purpose of a number, I thought.