Tony when Richard gets it right you will be kicking yourself for not thinking outside the box as it were, then it will all seem very obvious. I will put another view of it up this evening to be fair to those who are at work now. But you might be lucky Richard currently has internet connection problems
It has nothing to do with Admiralty communications (above or below water), Victorian Regulations, guided weapons, field latrines & all the old favourites. :-D