As far as I know all members of the British Armed Services and of the Police force have to pledge allegiance to the Queen, my question is ,Do all Members of Parliament have to do the same ? I can't imagine left-wingers wanting to do so.
They do have to swear allegiance. I think their refusal to do this is why Sinn Fein do not take their seats at parliament. I know in Scotland, one of the SSP MPs - Rosie Kane - took her pledge to the queen with "My oath is to the people" written on her open palm.
They all ought to take an oath of allegiance to us, the people , who pay for the whole ever-expanding ... yes, trough is the best word for it, loosehead.