NotSpaghetti
Mollygo - my maiden name was longer than the one you discussed.
Most people I know with long names don't sign with the whole of it. I used only some of mine in my signature - and though I took my husband's name I still abbreviate my first name and only use an initial as a middle one.
I asked the parents what they wanted, reminding them that their child would need to write their whole name on exam papers, starting with the Y2 SAT. About half way through Y1 I was informed that child X was now to be known by her 9 letter first name and her 8 letter surname. It wasn’t a problem for me, but it was lucky the girl was quite good at letter formation. In class she was known by a short form of her first e.g. Ginny, for Guinevere as originally requested by her parents.
I’d still like to hear examples of what happens when two db surnames marry. If they’ve kept both names because they value each equally.