[1] The Libellus was reproduced in its entirety by Bede in his Historia ecclesiastica gentis Anglorum, whence it was transmitted widely in the Middle Ages, and where it is still most often encountered by students and historians today.

[2] Before it was ever transmitted in Bede's Historia, however, the Libellus circulated as part of several different early medieval canon law collections, often in the company of texts of a penitential nature.

The Libellus is a reply by Pope Gregory I to questions posed by Augustine of Canterbury about certain disciplinary, administrative, and sacral problems he was facing as he tried to establish a bishopric amongst the Kentish people following the initial success of the Gregorian mission in 596.

[7] Augustine's original questions (no longer extant) would have been sent to Rome around 598, but Gregory's reply (i.e. the Libellus) was delayed some years due to illness, and was not composed until perhaps the summer of 601.

[12] This hypothesis is supported by the surviving manuscript and textual evidence, which strongly suggests that the Libellus circulated widely on the Continent for perhaps nearly a century before finally arriving in England (see below).

Still, the exact time, place, and vector by which the Libellus arrived in England and fell into the hands of Bede (and thence his Historia Ecclesiastica) is still far from certain, and scholars continue to explore these questions.

The Libellus consists of a series of responses (responsiones) by Gregory to "certain jurisprudential, administrative, jurisdictional, liturgical and ritual questions Augustine was confronted with as leader of the fledgling English church".

But in the most widely known version (that reproduced in Bede's Historia Ecclesiastica) there are nine responses, each of which begins by re-stating or paraphrasing Augustine's original questions.

[22] The eighth response concerns what a pregnant, newly delivered, or menstruating woman might do or not do, including whether or not she is allowed to enjoy sex with her husband and for how long after child-birth she has to wait to re-enter a church.

[24] An additional chapter, not included by Bede in his Historia is known as the "Obsecratio": it contains a response by Gregory to Augustine's request for relics of the local British martyr Sixtus.

[28] Klaus Zechiel-Eckes has even suggested the first half of the seventh century as the date for when the addition was made, that is only shortly after the Bobiensis’s initial compilation and at most only fifty years after Gregory's death.

[30] On the strength of Bede's word alone many later historians have claimed that the Libellus reached Augustine in a timely fashion;[31] however, as mentioned above, recent scholarship has brought this assumption into serious question.

In any event, some version of the letter seems to have been available in England by the late seventh century, for it was then that it was quoted by Theodore of Tarsus, Archbishop of Canterbury, in a series of judgments known today as the Paenitentiale Theodori.

[33] Elliot has speculated that Theodore introduced a Bobiensis-type collection to Canterbury in the second half of the seventh century, and thereby finally delivered the Libellus (as part of the Bobbiensis) to its originally intended destination.

Boniface also requested Nothhelm's opinion on the document's authenticity, for his own inquiries at the papal archives had failed to turn up an official "registered" copy of the letter there.

His failed attempt to locate a "registered" papal copy of the Libellus presumably suggested to Boniface the possibility that the document was spurious and had in fact not been authored by Pope Gregory I.

But this was perhaps due as much to the fact that seventh- and eighth-century canonical authorities (especially popes) so frequently conflicted on this subject, as to Boniface's own interpretative error.

[54] The upshot of Deanesly and Grosjean's research was that the Libellus was quasi-authentic: while not a genuine work of Gregory I, it was nevertheless based extensively on authentic Gregorian writings.

[55] Deanesly and Grosjean's thesis was addressed and refuted by the textual research of Paul Meyvaert,[56] following whose work most scholars have come to accept the Libellus as a genuine letter of Gregory.

[62] In 2008 Ubl not only showed that the marriage chapter was in fact authored by Gregory, but he also explained exactly how it was the Boniface and later historians came to misunderstand its meaning.