So, Ms Smith and Mr Jones are in love, and have the big white wedding. But it would too, too archaic for Ms Smith to take his name and become Mrs Jones. How patriarchal! So they keep their own names, which is entirely fine.
Then they reproduce… young Master… well, there’s the rub. He can’t be simply Jones… how patriarchal! So the simple and obvious solution is the double-barrell. Sounds kinda classy, too. Young Master Smith-Jones, and a little later his sister, Miss Smith-Jones… or possibly Jones-Smith, just to keep the author order fair.
This is all terribly egalitarian and good, and I’m a big fan of it.
But time passes on, as it will. Young Master Smith-Jones has grown up, gone out into the world and fallen in love… with the daughter of similarly enlightened parents, Miss Knightsbridge-Humperdinck.
They marry, keeping their names, and in due course reproduce. Young Miss Knightsbridge-Humperdinck-Smith-Jones. A bit of an issue at school, and filling in forms in the space provided, but doable, I guess… Until, in the course of time, she too grows up, meets and falls in love… with young Mr Allibrandi-Tompkinson-Edwards-Fahd.
And they marry and give birth, and…
Clearly this system needs a little more work.