I don't know who writes CAP 413, whether it is a committee of Health and Safety individuals, or oen eprson, but there are a few odd things about it. Many of these get changed at the next edition, so for about 5 years one would get "shot" for saying something a particular way, and then suddenly what you have been saying all along is the right way after all!
Actually, does anyone know who (specifically) does write CAP 413, as I'd like to discuss something with him/her. (Could phone the CAA, but I am sure someone here knows.)