Aren’t these just Special Collections?
Well, yes, mostly. But RLUK wanted to emphasise that universities often hold collections which fall outside the standard Special Collections remit e.g. other library collections, data sets, research outputs, or objects. These too may have qualities which mean that their parent organisations and wider society should value and support them. Not to mention that in some organisations, Special Collections includes archives, in others not, and sometimes they are the collections which are neither old books nor archives.
U & D (I find) are useful terms when discussing collections held in universities, whether traditional “Special Collections” or not. We’re not suggesting that universities start using them instead of “Special Collections”: too long for everyday use, U & D Collections would become UDCs and then we have UDC Librarians and the like, UDC Reading Room etc, not helpful for users!
I’ll be interested to find out what librarians, archivists, and all the other people who will be involved with this project make of the name.