The date of the cross and the translation of its runes have always been controversial. However, it is generally believed to date to the late 7th or early 8th century and may commemorate the early Anglo-Saxon kings of Northumbria. F M Stenton in Anglo-Saxon England (1974) says the cross commemorated Alhlfrith, son of Oswiu, and his wife, Cyneburg, daughter of Penda.
Some scholars have suggested care should be taken as the evidence is unreliable and changes may have been effected by over-ambitious cleaning of the stone in the mid-19th century, and erroneous or deliberate re-cutting of the inscriptions.
Essay 5, The Bewcastle Cross in Runes and Runic Inscriptions: Collected Essays on Anglo-Saxon and Viking Runes by Raymond Ian Page & David Parsons, Boydell & Brewer Ltd, 1995.
It is often twinned stylistically with the Ruthwell Cross in Dumfriesshire, now preserved inside Ruthwell Church. This is carved in a very similar style and carries both Latin and runic inscriptions.
(The Corpus of Anglo Saxon Stone Sculpture Volume 2, Chapter 7, The Bewcastle Cross and its Context by R.J.Cramp 1988).
Some of the controversy regarding the translation of the runes on the cross can be read in Some accounts of the Bewcastle cross between the years 1607 and 1861 by Cook, Albert S. ed. (1914).
William Nicholson visited in 1685 and reported the main inscription as being so weathered as being almost unreadable. Weathering is not the only cause of damage to the cross. It may well have undergone deliberate attack, and has certainly suffered from the attempts of scholars of at least two centuries to clean, examine and record the texts engraved.
The Rev. John Maughan, Rector of Bewcastle, was clearly facinated by the cross. In 1857 he read the word Alcfrid in its runes and assigned it to about 670.
The buds blossoms and fruit have been so carefully and exquisitely deliniated by the chisel of the workman, and are so faithfully preserved, that they seem as if they were things only just starting into life.
On several occasions Maughan was taken in by practical jokers living in the neighbourhood of Bewcastle, who faked antiquities and brought them to his notice. Two of these fakes were runic inscriptions, though the runes used in them were Scandinavian. These were the Barnspike [Barron's Pike] inscription ‘found’ in 1864 and the text ‘found’ at Hessilgil [Hazelgill] Crag in I872. Both were reported to learned societies by Maughan. They were recognized as forgeries independently by Calverley-Collingwood and R. S. Ferguson, the latter claiming that it was common knowledge in the Bewcastle district that the inscriptions had been faked.
When deciphered, the runes appeared to support an old Cumberland legend, published by John Maughan in 1857, but itself disproved.
Notes on the early sculptured crosses, shrines and monuments in the present diocese of Carlisle. Edited by W.G. Collingwood (1899).
I also failed to find the inscribed rock at Hazelgill Crag, 1km to the north of Barron's Pike, but had given up by then as the appeal of chasing fakes had disappeared with the physical nature of the terrain.
A runic inscription on Hessilgill Crags: Murchie's Cairn. Transactions of the Cumberland & Westmorland Antiquarian & Archaeological Society, vol.1 p.318).
This time he read:
Askr wrote this in memory of the son of his companion Hessil.
He failed to notice the pristine nature of the runes and was clearly taken in by references to both Hessil (the old name of the crags) and Askr, which he related to ASKERTON,
"the name of one of our noted Border Castles, and probably the ancient residence of this ASKR, whom, with his friend Hessil, we may suppose to have been an old Norse pirate, and to have settled in this district and given his name to it."
The poor Rector of Bewcastle seemed quite gullible and easily prone to such mischief. He was also caught out by a fake Roman inscription found in 1859 which supported his ungrounded theory of a Roman Fort at Lanercost.
A forged rock inscription near Lanercost by R G Collingwood TCWAAS vol.29, p.91-7, 1929.
"The forger was certainly not Maughan himself, but someone who wished to take him in, and did it in exactly the right way, by giving him a bait he was sure to swallow.
I may quote an acute remark made in connection with the greatest archaeological hoax on record :--
"on prend les sardines avec de la rogne, on prend les grives avec du genièvre, on prend les savants, à thèses avec le mirage de leurs théories."
https://en.wikipedia.org/wiki/Glozel
http://philipcoppens.com/glozel.html
Who the forger was, I do not know and do not wish to know; but I suspect that he was the same person who imposed on Maughan by forging the Runic rock-inscriptions at Barnspike and Hazelgill. These came to light in 1864 and 1872; they were eagerly accepted by Maughan and by Professor George Stephens of Copenhagen, to
whom he communicated them; and it was not until 1899 that their true character was announced by Mr.W. G. Collingwood, who exposed both frauds in Early Sculptured Crosses in the Diocese of Carlisle."
There is reason to think that Maughan was the victim, especially in his later years, of a series of practical jokes. Old roads, pavements, ruined forts (cottages) were found for him, by the zeal or roguery of his neighbors; and these runes are their creation. They are not the work of a Runic scholar; they were concocted by a clever Cumbrian who had read the Rector's papers, heard his talk, perhaps used his books, and, like his countrymen, laughed at enthusiasm and loved a joke.
(W G Collingwood 1899)