I suppose this is the best place to mention this, some late(ish) night services to Basingstoke have had a Security Guard [Someone wearing a jacket saying "Security"] and a Guard on in the past.
The "Security" Guard always sat in First Class and offers the ID he wears when tickets are inspected.
The Guard has never complained and asked him to move, so is he entitled to sit there?
PS: Haven't travelled at that time in six months...
I guess if this is where they always sit it's easy for them to be found if needed. Constant patrol might be intimidating and put people off travelling but by being in the same place that easily identifiable (e.g first class) then if trouble does surface the security guard can easily be found for support. This is just an assumption though