Suggesting that there should be security specialists on board a submarine or ship shows a lack of understanding of how the RN operates. By necessity personnel have to be multi-roled and the smaller the vessel, the more this is required. Every person on board a submarine (from Chefs to the Captain) is highly trained and has a unit-wide systems knowledge that is probably without rival in the UK armed forces. I wouldn't say this to a sun-dodger's face, but they are hugely impressive. It would be completely impractical to carry more people and whether you like it or not, guarding the submarine alongside is secondary to her primary duties - blowing **** up and intelligence gathering. The people that are involved in looking after the SM alongside (basically everyone) are fully trained - I don't think you could really ask a lot more than that.
Thomas Coupling - in response to the question about what this has to do with aviation... I hope you're asking the same about the other topics du jour in the military part of PPRUNE. A couple of examples: "Military Saluting Politicians" & "Enhanced Learning Credits". The answer is that it is a subject of interest to all military personnel, of which aircrew are a part and I would suggest that it is of even greater to members of the FAA. I think the subject is quite obvious from the thread title so my suggestion would be not to read it if you're not interested.