Geoffrey of Monmouth's largely invented Historia Regum Britanniae or the History of the Kings of Britain concludes its account of the early history of Britain with the events of the reign of Cadwaladr Fendigaid or Cadwaladr the Blessed; "the last king that ruled over the Britons" as the later Brut y Tywysogion would have it.
The last king of the Britons
According to Geoffrey's account, Cadwaladr succeeded his father Cadwalla as king but fell ill and a civil war broke out, when "the Britons .... quarelling among themselves made a wicked destruction of a rich country". For this were punished with "a grievous and memorable famine" as well as "a terrible pestilence, which in a short time destroyed such multitudes of people, that the living were not sufficient to bury the dead".
This triple sequence of disaster drove the Britons "to the countries beyond the sea". Cadwaladr himself fled to Brittany lamenting that the true agent of his nation's destruction was "the power of the Supreme King, whom we have never ceased to provoke". Britain "now freed of its native inhabitants" lay at the mercy of the Saxons and "that odious people, gathering together an innumerable multitude of men and women, arrived in Northumberland and inhabited the provinces that lay desolate from Albania to Cornwall", excepting only "the poor remain of the Britons who continued together in the thickets of the woods of Wales".
As Geoffrey put it;
From that time the power of the Britons ceased in the island and the Angles began their reign
Despite being forced to abandon Britain, Cadwaladr had not given up hope of being able to recover the country and "when the people had recovered strength" he began gathering together a fleet to transport himself and his men across the channel. It was then that "he was commanded by the loud voice of an angel to desist ftom the enterprise".
Cadwaladr sought the advice of Alan, the ruler of Brittany who consulted the available authorities such as "the eagle that prophesised at Shrewsbury and the verses of Sibyl and Merlin" and as a result advised Cadwaladr to heed the angel's warning. And so Cadwaladr took this advice "and went to Rome where he was confirmed by pope Sergius and died of a sudden illness".
The Prophecy of the Angel
Although the angel had informed Cadwaldr that "God was not willing that the Britons should reign any longer in the island" the angel also had a message of hope and predicted "that the Britons, by merit of their faith, should again recover the island, when the time decreed for it was come". Of course there were certain specific conditions that had to be met; the British "should be possessed of his relics and transport them from Rome into Britain" in addition to which "the relics of other saints should be found, which had been hidden on account of the invasion of the pagans".
This is a very nice story and perhaps one of the more readable portions of Geoffrey's work but it is worth remembering that his history, whilst now dismissed as fable, was for centuries widely accepted as being a true and accurate account of events. And in less outwardly rational and perhaps more credulous ages, omens and prophecies were taken seriously and there was a time when people studied the Historia in a search for clues as to what the future held.
Geoffrey's work included not only the Prophecy of the Angel but also the longer and more rambling Prophecy of Merlin, which fills the 3rd and 4th Chapters of Book VII of Geoffrey's Historia and like most prophecies can probably be interpreted to mean whatever you want it to mean. But one of the most telling and unambigous phrases in the Prophecy of Merlin was the prediction that "Cadwaladr shall call upon Conan and take Albania into Alliance. Then there shall be a slaughter of foreigners, then shall the rivers run with blood."; which gives the general drift of things.
Therefore since Cadwaladr was "the last king that ruled over the Britons" and the Angel had prophecised that "the Britons... should again recover the island", there was an expectation in some quarters that one day a descendant of Cadwaladr would rise to power and begin the "slaughter of foreigners".
This explains why the English kings started feeling nervous every time a ruler of some authority emerged in Wales and took such pains to crush them before they could fulfill the prophecy. They were naturally particularly concerned when that ruler was from the royal house of Gwynedd, who did indeed claim to be the direct descendants of Cadwaladr. It is also one of the reasons why Edward I awarded his son Edward, born at Caernarvon in 1284, the dignity of Prince of Wales at Lincoln in 1310. He was simply hedging his dynastic bets and trying to ensure that his son, a Welsh born Prince of Wales, could be seen as fulfillment of that very prophecy.
Every potential and actual leader of a Welsh rebellion such as Owain Llawgoch or Owain Glyndwr was seen as a potentially fulfilling the prophecy and even Roger Mortimer, 1st Earl of March who possessed that same magical link to the royal house of Gwynedd through his great-grandmother Gwladus Ddu, 'Black Gladys', daughter of Llywelyn ap Iowerth the thirteenth century ruler of Gwynedd and supposedly a direct descendant of Cadwaladr.
In the late fifteenth century, this ideas blossomed again. After defeat in the Hundred Years War and the loss of both Normandy and Aquitaine, after the turmoil and instability of the War of the Roses, the English were confused and were looking for redemption. Manuscripts supposedly detailing 'Merlin's Prophecy' were widely circulated; Geoffrey's work was scrutinised by both Yorkist and Lancastrian claimants eager to find something to bolster their contrasting claims.
As a result Edward IV, Henry VII and even Richard III conciously presented themselves as the heirs of Cadwaladr and posed as redeemer kings seeking to heal the wounds of discord. It is quite well known that Henry VII did so, he named his eldest son Arthur and what better fulfillment of the prophecy could there be than to have a King Arthur on the throne of England. But Edward IV did so as well, and indeed had a better claim to do so than his Lancastrian counterpart, whose Welsh descent only linked him to a former steward of the rulers of Gwynedd. In his dynastic propoganda Edward IV gave a great deal of prominence to his inheritance, though his grand-mother Anne Mortimer of that magical Mortimer link to Cadwaladr. He could explicitly portrayed himself as the fullfillment of the prophecy and as the heir of Cadwaladr and the heir of Brutus himself who supposedly founded Britain itself back in the mists of time.
Strangely enough therefore the Prophecy of the Angel matters in British History. It's the reason why the eldest son and heir of the British monarch is the Prince of Wales and the Prophecy mattered to both the Yorkist and Lancastrian claimants to throne, who sought to legitimise their claims to the throne of England by reference to their links with an eight hundred year old Welsh king and the fantasies of a twelfth century Breton cleric.
Quotations are taken from The History of the Kings of Britain by Geoffrey of Monmouth, translated by Aaron Thomson with revisions by J A Giles from In Parantheses publications, Medieval Latin Series, Cambridge Ontario 1999.
Jonathan Hughes Arthurian Myths and Alchemy (Sutton, 2002)