No it's not
in fact, the state is The United Kingdom of Great Britain and Northern Ireland - there isn't an English monarch, or a British one
In normal language there's certainly "a British monarchy".
Whatever the politics! It's the British Monarchy at the moment!
in fact British...
Prințul Andrei nu este
Mmmhhh... Liz two... So hot
isn't the monarhia fermecatoarA?
for adjectives ending in -or the feminine ends in -oare (fermecător / fermecătoare; asurzitor / asurzitoare; sclipitor/ sclipitoare, etc.)