Ordo Romanus Primus (ORP) is a descriptive account in Latin of the papal mass at Easter in Santa Maria Maggiore, probably at some time in the seventh or eighth century. It is the first such account, and differs from earlier evidence of the Roman rite by its relative disregard for the spoken text, which is usually only cited in ORP as providing cues for the ceremonial action. The 'action', however, is detailed, is often surprising, and gives a three-dimensional approach to a rite which, in its textual form, only tells the half of what was happening. The whole action is set on a large canvas, so that the account starts with the procession of the papal household from the Lateran. As Alan Griffiths put it 'the nature of ORP is to be a key to ritual business, not to text', and he adds 'one might describe it as an "events management" document.'

There has been no full edition of the text in English since that of Atchley in 1905, and his translation has today a highly dated look to it. Alan Griffiths has drawn upon the Latin text collated by Michel Andrieu in his French edition of the ordines Romani in 1948, and has provided his own fresh and contemporary translation of it into English, running in parallel columns with the Latin. It makes a valuable addition to the series of Joint Liturgical Studies which have made such a large range of patristic liturgical materials available to students who work largely in English.