I think Archimedes has it absolutely right, if they have earned their rank at the level of RN Captain and above, or equivalent, then let them use it. The example of the two captains he refers to, though fictional, does reveal how some ex officers (although of course both of those chaps were merely Army captains) are perceived by the public. On the whole though, I believe it is a dangerous game advertising your previous service to a country which at best doesn't care anymore and at worst will have you targetted for being associated with some 'military outrage' reported by the excellent and balanced media we seem to have here.
Before anyone from the Army has a go, I mean 'merely' in terms of how far up the tree the guys are, not that Army commisions should not receive the same respect as the other services, although one does wonder where the inspiration for Peacock and Mainwearing came from.
Bugger, I'll go and find a spade, I think my hole needs digging deeper
