Blake’s poem, Jerusalem, later put to music by Parry and orchestrated by Elgar, refers to the legend that Jesus once came to Britain as a tin trader with his “Uncle”, Joseph of Arimathea. The story originally was just about Joseph alone, and even that seems to be relatively late, replacing or adding to another myth that he had come to Britain after the Crucifixion.
In that earlier story, Joseph had come to Glastonbury and built the first Christian church in the British Isles. He had also planted his hawthorn staff in the ground, and it miraculously took root and bloomed on Christmas day. The hawthorn continued to grow, and to brazenly bloom twice a year, until it was chopped down by Puritans in the 1640s. However, cuttings had been taken over the years, and many descendants exist today, still doing their mutant blooming thing.
In 1184, Glastonbury Abbey burned down. “Miraculously”, the hard-up monks discovered the graves of King Arthur and Guinevere, and income from tourists enabled them to rebuild in fine style. A lead cross dug up from Arthur’s grave identified it: “Here lies buried the famous King Arthur in the Island of Avalon.” Unfortunately, the cross disappeared (possibly the Puritans again) but not before a Seventeenth-century antiquarian had sketched it. From the style of lettering it doesn’t look like an 1100s forgery, but not as old as Arthur either.
I’m not clear on whether the link between Joseph of Arimathea and Arthurian myth came before or after he became associated with Glastonbury. Either way, the Medieval romances made Joseph the first keeper of the Holy Grail. The Nanteos Cup in Wales (but said to be from Glastonbury) has long been claimed to be the Grail, being of olive wood, and as Indiana Jones pointed out, a simple cup that might have been owned by a carpenter. Well, I have a simple spoon made out of olive wood and it’s not a religious relic. (Although, it will be when I’m dead, obviously).
There’s not the slightest historical information about Joseph, apart from the part in the Gospels where he provides his family tomb for the body of Jesus. Details about his being Jesus’s uncle, about his being a tin trader, about him spreading Christianity and bringing it to Britain; these have all accumulated over the ages. Or to be less charitable, it’s all made up.
But traders from the Eastern Mediterranean did come to the British Isles to buy tin, and it happened during two specific periods. First, the Phoenician commercial empire had links to Britain in “Bliblical” times, from about 1000 BC to 300 BC. (Unfortunately, a few hundred years before Joseph.) Then, as archeology indicates (but undocumented in history), trading routes were opened up again in the Fifth Century AD. The time of Arthur.