The Stowe Missal, so called because it was once in the ducal library at Stowe, is insufficiently esteemed among those with an interest in Roman Liturgy.
It is of profound interest because it is a unique manuscript witness to some features in the Roman Rite before S Gregory the Great made changes in it. Although the ms dates from the last decade of the eighth century, it was clearly copied from an exemplar of before the 590s. The main deviation from the 'Gregorian Rite' is that the Fraction is in the 'Ambrosian' position, before the Lord's Prayer. And S Andrew, something of a patron for Pope Gregory, has not yet entered the Stowe Libera nos.
The Rite begins with a Litany. When I wrote a paper for the Proceedings of the Royal Irish Acaemy, some two decades ago (Kerry and Stowe Revisited), I was puzzled by this initial Litany. It is not required by the need for an Intercession; the Stowe Intercession comes between the the Epistle and the Gospel (and, of course, there are the Nomina and the intercessory paragraphs in the Canon Romanus). Its quality is penitential.
Now, having thought my way this week through the concept of lustratio and the Rogation processions, I now have ... at least! ... a hypothesis.
The monastic and ecclesiastical sites which so proliferate in Ireland's most beautiful county, Kerry ('the Kingdom of the West' memorialised in a poem by Sir John Betjeman), normally have a wall or other geographical feature defining the extent of the claustrum.
Just like such processions as those in England and elsewhere at Rogation-tide, I believe that these defining features delimit and set apart the Sacred from the Profane; 'our' territory as against that of outsiders. Just like the Rogation Processions, the religious enclosures in Kerry were, I surmise, seen as calling for ritual and periodic reassertion on the part of their community.
G G Willis (1968), in his account of the rites of Consecrating churches in Latin Christendom, makes a number of references to the use of litanies. Stowe, or its archetype, may originally have been compiled for the sacring of a new religious establishment: its Hanc igitur makes especial mention of the person who has donated the site.