The question of Christianity in England is equally unsettled. Gildas wrote in the sixth century: “These islands received the beams of light … in the latter part of the reign of Tiberius Caesar, in whose time this religion was propagated without impediment or death.” The point about this is that Tiberius died in AD 37. Nor does Eusebius contradict this date, though scholars of course have difficulty explaining. Nevertheless, by AD 1999 Tertullian, listing the many peoples to whom the religion of Christ has come, can include, “the place of the Britons, which are inaccessible to the Romans.”
-Celtic Christianity, p.13, intro by Christopher Bamford
The extremely early appearance of Christianity in Britain and Ireland is a curious piece of history. The theory that is spread via a group of adventerous Syrian monks, bypassing France and Spain by boat, has gained traction in recent years. This accounts for the eastern flavor still detectable in the heirs of the Celtic church today. I think one reason it took so long for scholars to take this idea more seriously is that it’s become mixed up or conflated with the much later myth about Joseph of Arimathea bringing the Holy Grail to Briton shortly after the ascension of Christ.
It’s curious that I find the two most interesting pockets of Christian history to be that of Ireland and that of Ethiopia, another early adopter who was, as Tertullian put it, “inaccessibe to the Romans”. In fact, Ethiopia was still inaccessible to the Romans (or Italians) in modern times, having their secular 1896 invasion squashed and their attempt at occupation in the 1930s was short-lived as well. Though buried under centuries of cultural customs and changes, something peculiar of the earliest saints remains in their tradition – something no longer present in the bulk of the west – something you can’t quite put your finger on – but something good.