May the Queen Rest in Peace; God Save the King

This most famous Coronation Anthem is evidently based upon the following Magnificat antiphon, used in the Roman Breviary on the Saturday before the 7th Sunday after Pentecost:

Aña. Unxérunt Salomónem Sadoc sacérdos et Nathan prophéta, regem in Gihon, et ascendéntes læti dixérunt: Vivat rex in ætérnum. (Cf. 3 Reg. 1, 45)

Traditionally sung after High Mass in England:

V. Dómine, salvum fac regem [nostrum Cárolum].
R. Et exáudi nos in die qua invocavérimus te. (Cf. Ps. 19, 9)

Orémus.

Oratio.
Quǽsumus, omnípotens Deus: ut fámulus tuus Cárolus rex noster, qui tua miseratióne suscépit regni gubernácula, virtútum étiam ómnium percípiat increménta; quibus decénter ornátus, et vitiórum monstra devitáre, [in tempore belli: hostes superáre,] et ad te, qui via, véritas et vita es (cf. Joan. 14, 6), [cum regína consórte et prole régia,] gratiósus váleat perveníre. Per Christum Dóminum nostrum. R. Amen.

[1962 MR: Qui vivis et regnas in sǽcula sæculórum. R. Amen.]

NOTE

The 1962 Roman Missal (see the text of the Oratio pro Rege among the votive prayers) changed the traditional ending from Per... to Qui vivis..., as seems logical, for given that Christ told us that he himself is the way, the truth and the life, and as that phrase is used in the body of the prayer, so it would seem that the prayer is addressed to God the Son; however, traditionally the prayer was understood as addressed to God the Father, despite this – I seem to recall the Sacred Congregation of Rites, when consulted on this point, insisted on retaining the Per... (though that was in the days when the Vatican answered dubia rather than gaslighted the faithful, but I digress). 

I have indicated in square brackets the additional phrases used in the traditional versicle and collect that are not given in the Missal. 

A number of other online sources incorrectly read incrementum not incrementa, but the Latin in the Missal and in older prayer books published in the reigns of earlier kings confirms that the plural is wanted, not the singular - “increases of all the virtues” not “an increase of all the virtues” is what is prayed for. I suspect that some persons wrongly thought that incrementa agreed with the gender of the monarch, and thus had to be changed from feminine to masculine, whereas it is in fact neuter plural.