martyrdom · 300 · Verulamium
The story is told by Gildas and then by Bede: Alban, still a pagan, sheltered a priest fleeing the persecution, was converted by watching him pray, changed clothes with him when the soldiers came, and was taken and executed in his place. The details that stick are the ones a legend usually loses — that he was not yet a Christian when he acted, and that the mercy came first. The date is the problem. Bede puts it under Diocletian, which would be 303 or after, but Britain was under Constantius, who is generally reported not to have enforced the edicts there; so scholars have argued for the Decian persecution, for Septimius Severus, or for a local action under no persecution at all. This dataset dates the event 300 and grades it traditional, which is the honest position: the martyrdom is old and well attested as a cult, and the year is not known. What is remarkable is the continuity. There has been a shrine on that hill since at least the sixth century, when Germanus of Auxerre visited it, and the abbey and the town still carry his name.
What is the first British martyrdom, and can it be dated?
Alban, at Verulamium — and no, not securely.