(I'll regret this in the morning...)
I often talk about this opera in the following terms.
There is a fellow, a Lord, who is engaged in diplomacy, with an otherwise 'difficult' part of the globe..We don't have to really talk about it, let's call it "Fairyland". He falls in love with an equally young party planner in the Fairyland court. Now, because of what might be called 'conflict of interest', she is not to have anything but a superficial relationship with any man not from Fairyland who might interest her.
So, he tells her that it doesn't really matter, that Fairyland is going to soon become a British Protectorate, and that, in any case, she shouldn't worry...They get married on British soil.
Except that the deal falls through. Iolanthe is pulled before an angry Queen, who immediately demands her death. She pleads that she is pregnant, and her sentence is commuted to life imprisonment, on condition that she never again speak to her husband. Her friends arrange for her son to be, in the language of the time "brought up by a bank", until the age of 25. He's handsome, charismatic, not-too-bright, but charming, and..well, hello, Dad!
Now, understand, I'm not even talking about the action of the play!Anyway, the son, Strephen, falls in love with Phyllis, the "ward of the state" that his lecherous old father intends on marrying, and then...
The Queen shows up. She explains that well, her son is going to take, as is his right, his place in the House of Lords. And that he's pretty much going to be, with all the coaching he's gotten in Fairyland, one of the best and most persuasive speakers of his generation, or for that matter, ever! And he gets them to pass a lot of important, though otherwise noninteresting, bills. But he still lives for Phyllis. On the other hand, Iolanthe sings one of the best examples of anyone putting the emotional screws on anyone: veiled, she describes to him, not the details of their wedding night, but the contents of their closet. If he cannot understand that his not keeping it in his pants has completely ruined one life, let him let his son marry whom he will.
All is solved when the Queen signs the treaty, and decides on the clause that "all shall be put to death who do not marry a Peer."