"Imploret, clementissime Domine, nostris opportunam necessitatem opem devote a nobis prolata meditatio, qua sanctus olim Joannes Chrysostomus, in hac basilica conditus, te cum beatissimis Apostolis Petro et Paulo repraesentavit sic colloquentem: Circumdate hanc novam Sion, et circumvallate eam: hoc est, custodite, munite, precibus firmate; ut quando irascor in tempore, et orbem terrae concutio, aspiciens sepulcrum vestrum nunquam desiturum, et quae libenter propter me geritis stigmata, iram misericordia vincam, et ob hanc percipiam vestram intercessionem. Etenim quando Sacerdotium et Regnum video lacrymari, statim quasi compatiens ad commiserationem flector, et illius meae vocis reminiscor: Protegam urbem hanc propter David servum meum, et Aaron, sanctum meum. Domine, fiat, fiat, Amen, Amen."
That is the text of the prayer of which I yesterday provided a translation. It follows penitential prayers and versicles and responses imploring Apostolic intercessions. Then comes the exquisite and ancient prayer which serves as the Collect of the Vigil Mass of SS Peter and Paul ... and, finally, Imploret.
Somebody out there will be able to explain it all. To me, its oddities include the combination of SS Peter and Paul, who are not buried in the same basilica ... was the prayer to be said at the sepulcre of each of them? Is the prayer connected with Pope Urban's Consecration of the [new] Basilica of S Peter? It surely can't have been part of the actual service of Dedication, because the Dedication of even quite a modestly sized church is a lengthy business, and no sane Pope (or MC) would want to add stuff.
Does 'Regnum' simply nod politely to Ancien regime polity, or does it mean the Papal States?
Most interesting to me is the theological implication that Urbs Roma is an ancient and venerable Sacramental in which the City represents and carries the symbolic weight of the city of YHWH, the Sion of God. That idea, of course, certainly goes back to the composition of the Mass of Laetare Sunday and probably to the Empress Helena.