It is well known that this University has always regarded itself as immune from the jurisdiction of the Kings of Arms; both University and Colleges have ever devised and adopted into use their own Arms; often simply using the achievement of a Founder. My wife's College uses the Arms of the father of its founding principal, Dr Eleanor Plumer; he, as a distinguished Field Marshal and First World War general, had been granted a Coat of Arms including a sword surrounded by a laurel wreath ... a striking heraldic adornment for a Women's College!
When, in 1548, the University Press was finally firmly established (after two rather infirm earlier establishments going back to 1478) with Joseph Barnes as Architypographus, the first thing he did was to have a splendid block made of the University Arms. These were then, as they are now, three ducal coronets upon a field azure and, between them, an open book. But, whereas the words on the book now read Dominus Illuminatio Mea, from Barnes' time until at least 1658, the 'motto' was Sapientiae et Felicitatis. I expect some writer has explained all this; if a reader can point me in the direction of information, I would be grateful.
If I had anything to do with the (technically illegal) assumption of Arms by Catholic entities in England, I would behave rather differently from whoever currently does cook up such designs (it is my confident guess that the College of Arms has had little to do with these productions). The Ordinariate, for example, uses the Priory of Walsingham impaling Newman, which would normally imply either that the Prior of Walsingham had married a Miss Newman, or that a member of the Newman family held the office of Prior. The Anglican College of Guardians of the Shrine did distinctly better in 1945; I suspect Fr Fynes Clinton (who paid the fees) may have had a lot to do with the design. The Kings of Arms granted Arms consisting of the Priory of Walsingham (Argent, upon a cross sable, five lilies of the first slipped and seeded proper) differenced with a canton (azure, charged with the Holy House or). A correspondingly elegant composition for the Ordinariate would have been the Priory of Walsingham differenced with a canton of Newman.
I think I rather like the use of cantons to do differencing. I can think of an example that goes back as far as the Roll associated with the Siege of Caerlaverock in 1300. It means that neither of the two coats concerned is deprived of its integrity. Allen Hall, for example, would look well if (given its origins) it were Oxford Ancient (i.e. with the words Sapientiae et Felicitatis!) differenced with a canton of Allen ... that is, his very jolly little conies!
Gumming a couple of coats together by means of impalement, which in heraldry most commonly implies the sort of temporary association that goes with a marriage (or the metaphorical marriage where an office-holder impales his arms of office with his own arms), seems unsophisticated if not down-right plain misleading!