The plot follows the fictional English King Magnus as he spars with, and ultimately outwits, Prime Minister Proteus and his cabinet, who seek to strip the monarchy of its remaining political influence.

Shaw's preface describes the play as: ...a comedy in which a King defeats an attempt by his popularly elected Prime Minister to deprive him of the right to influence public opinion through the press and the platform: in short, to reduce him to a cipher.

The King's reply is that rather than be a cipher he will abandon his throne and take his obviously very rosy chance of becoming a popularly elected Prime Minister himself.

He modelled the enigmatic and pivotal character Orinthia, the King's mistress, on Mrs. Patrick Campbell, the actress who had created the role of Eliza Doolittle in Shaw's Pygmalion.

[3] The "Powermistress-General" is said by the biographers of Beatrice Webb to be modelled on Susan Lawrence, an old colleague of Shaw from the Fabian Society.