Our knowledge of these events is based on the work known as de Vita Germani (the Life of Germanus) written sometime in the early 490's AD and is therefore a reasonably contemporary record of events.
Germanus' First Visit
Germanus was the bishop of Auxerre in Gaul and his visit to Britain was prompted by the fact that the Pelagian heresy had taken deep root within the Romano-British church of the 5th century. A Romano-British cleric by the name of Palladius had requested assistance from Pope Celestine to combat the heresy. A Council was convened at Troyes in Gaul and Germanus together with Lupus bishop of Troyes itself, were selected to act as the papal representatives on a mission to return Britain to orthodoxy.
We know that Germanus departed from Boulogne, probably travelled through Kent, preaching as he went, and arrived, very probably in Londinium (modern London) to engage the Pelegian heretics in debate. Although the de Vita Germani gives no clues as to when this happened, the Chronicles of Prosper allow us to accurately date this event as it states for the year 429 AD;
Agricola, a Pelagian, the son of the Pelagian bishop Severianus, corrupted the British churches by the insinuation of his doctrine. But Pope Celestine sent Germanus, bishop of Auxerre, as his representative, and having rejected the heretics, directed the British to the catholic faith.
(Which, of course, is a very big deal to historians of this period in British history, as it is one of the very few accurately dateable events that currently exist.)
has sufficient rhetorical gifts to trounce the arguments of the heretics
and win the debate, therefore ensuring that the Romano-British
church remained true to the Catholic
He then goes on to visit the shrine of the martyr Alban at Verulamium (modern St. Albans) and on discovering that the Anglo-Saxons and the Picts have joined forces to make war on the Romano-Britons, Germanus takes charge of the defending forces. He baptises the troops (1) and teaches them to shout "Alleluia" at the enemy. This is sufficent during the course of the engagement to frighten the invaders, who promptly run away. Hence this is known as the Alleluia victory (2), and as the de Vita Germani explains;
The bishops were elated at the rout of the enemy without bloodshed and a victory gained by faith and not by force.
The de Vita Germani ends the episode with the return of Germanus to Gaul and the comment;
Thus this most wealthy island, with the defeat of both its spiritual and human foes, was rendered secure in every sense.
Germanus' Second Visit
Germanus made a second visit, again supposedly to combat Pelegianism.
Opinions differ as to when this took place, but 447 AD seems to be the favourite. The de Vita Germani has less to say this time; Germanus makes contact with one Elafius, who is described as regionis illius primus, some kind of local king or tyrant, discovers that little evidence of the Pelegian heresy and goes home again.
This has led some to speculate that Germanus had been sent by Aetius in response to the Appeal of the Britons of circa 446 AD to report on the situation. Even if this was the case, nothing ever came of it. Germanus died in 448 AD and Aetius was murdered in 454 AD.
The historical importance of these events
The de Vita Germani was, of course, not written as history, rather hagiography and it mostly consists of accounts of the sundry miracles attributed to Germanus, and little in the way of a historical detail.
Its importance lies less perhaps in the detail of what happened, and more in terms of the picture it paints of Britain in the early 5th century after the departure of the Romans. During the first visit, the de Vita Germani describes the arrival of the leaders of the Pelegian faction at the debate with Germanus in the following fashion;
They came forth flaunting their wealth, in dazzling robes, surrounded by a crowd of flatterers.
As the historian Peter Salway(3)
we are observing not a ruined class living in bondage to barbarian masters, nor even a few fortunate survivors, but a substantial body of men of influence who carry weight both with their personal following and the community at large
seem therefore to have coped reasonably well in the twenty years since the dismissal of the Romans
. The island continues to be threatened by barbarian
incursions but has succeeded in maintaining an independent existence.
Part of the Sub-Roman Britain project, where sources are detailed.
(1) Which of course leads to the point that these soldiers were obviously not previously Christian. Either native paganism was still fairly widespread in 5th century Britain or perhaps they were even Germanic mercenaries.
(2) Generally speaking, historians seem to accept that some sort of battle took place, (or at least believe that it is possible) without necessarily accepting that the victory was achieved in quite the manner described.
(3) Roman Britain - Oxford University Press 1991 p465