"My nationality on the passport is described as 'british citizen' ."
Well that's a larf innit! Where's the constitution? There isn't one! You have no rights, really. We come from a Kingdom, not a republic, so you can't be a *citizen* ... we are all *subjects* ... She could have your head chopped off tomorrow if she really wanted to :-)
And to be pedantic to the pedant I bet it says 'British Citizen" and not 'british citizen' :-)