There's a problem with history. It's like quantum physics, in that the results you get tend to depend on where you happen to be standing.
In other words, history is all about perspective.
The historian Michael Wood wrote an interesting piece for the BBC News Magazine to accompany his new series about the history of Britain. Like many historians, Wood starts his history with the Romans.
There is something of a perception among historians that the ancient Britons were useless. They just sat around in the mud, scratching their backsides and waiting for the Romans to come along and show them how to do things.
Of course, the Britons rejected the advances of Julius Caesar in 55 BC. But ninety years later, there were a fair few British chieftains - mostly in the south and east of Britain - who were familiar with life on the Continent and who saw the potential of being clients of Rome. For the chieftains, this could mean new, undreamt-of levels of luxury, just as long as they consented to Roman domination. So when Claudius mounted his invasion, there were some tribes who effectively welcomed them in and no doubt stood in awe as a squadron of elephants entered the country.
The Romans were less welcome in the west and the north, and they failed to subdue the Scottish Highlands. The Roman soldiers coined a name for the tattooed tribesmen of the far north: they called them pictii - the Painted Ones. In fact, the native Britons as a whole seem to have had a preference for tattoos, and for two or three centuries it is probable that the native population was divided into those who shaved (in the Roman style) and those who decorated their bodies.
In his piece for the BBC, Michael Wood compared the collapse of Roman rule, and the withdrawal of the legions - a process that was more or less completed by 409 AD - with the current economic crisis in Europe. He made some salient points, one of them being about social inequality: 'in the 300s the big land-owning aristocrats who often had fantastic wealth, contributed much less than they had in the past to defence and government.'
There is indeed evidence that the wealthier members of Romano-British society resented paying for the privileges which their ancestors had sought. A phenomenon we have seen much of in more recent times.
The Roman Empire collapsed - but rumours of Britain's demise were a tad premature. Yes: hard times lay ahead. As Wood points out, the population of Britain shrank from a high of about four million to just one million in the 500s, as a result of climate crises, famines, plague and warfare. But Britain would remain Britain until many years after the Romans left.
Even in the south, which fell first to the waves of Germanic immigrants known, collectively, as the Saxons, the decisive blow didn't fall until the Battle of Dyrham in 577, when the Saxons fought their way through to the River Severn, cutting off the Britons of the south-west from those of the Midlands. That was nearly 170 years after the last Roman legion withdrew from British shores. It was also right in the middle of the lifetime of Arthur.
However, Arthur was not in the south (no matter how hard many scholars want him to have been). He was in the North. And the Men of the North were fighting back against the Anglian settlers of what is now Northumberland.
When the Saxons were breaking through to the Severn in the south, Arthur was battling against the Ulaid warriors of Ulster in central Scotland. Three years later, he won a major victory over the southern Picts. And by 590, his alliance of British and Irish warrior-princes had driven the encroaching Angles back to the sea. A British army had the Germanic warriors pinned down at Lindisfarne while, a little further down the coast, an Irish contingent was besieging the Anglian stronghold of Bamburgh.
That was when treachery struck from within Arthur's own ranks.
Four years later, in 594, Arthur fought his last battle and was betrayed by those he trusted. By the following year, the resurgent Angles had overrun much of the North. Britain was finished.
This happened almost 200 years after the Romans departed - and so we should be wary of any claims that Britain descended into absolute chaos the moment the well-organised, militarised and bureaucratic Romans left us to our own devices.
One point Wood makes in his BBC piece is of enormous interest. He refers to Edward Gibbon, the Victorian author of the classic Decline and Fall of the Roman Empire, and notes that Gibbon - rather unusually, given the age he lived in - blamed the collapse of British society, not only on the barbaric invaders from across the North Sea, but on Christianity. In Gibbon's view, by focussing on a better world, a future paradise, Christianity undermined the Britons' attempts to deal with the crisis they were actually caught up in.
There is something in that. You will still hear those who - speaking from a rather imperialistic perspective - praise the Roman occupation and imagine that Christianity was thoroughly settled as the one and only religion in Britain by the time the Romans left. This is the simplistic view of history: the Romans came, dragged us up out of the filth, and then Christianity finished off the job by making us civilised. But it wasn't really like that.
At least where Arthur was concerned, the belligerence, intransigence and ambition of the early Church caused his downfall. There is evidence that the early Church destroyed anything it could find relating to the Celtic intelligentsia - the 'Druids' - and rewrote history to make its own triumph seem inevitable.
The supporters of the early Church were, in many ways, the same people who had so admired the Roman Empire. The antagonists of the early Church were, by and large, those who preferred the native traditions and saw Britain's future, not as a far-flung province of the reborn Empire (the Church of Rome) but as an independent nation in its own right. As we know, the Church won. It certainly played dirty, and then did everything it could to cover its tracks.
Hence, the Dark Ages - a period in British history when nobody really knows what was going on, because the Church controlled the information. But the problem goes much further back than that. The Roman occupation distorts our view of ancient Britain, and the rise of the Church distorts our view of post-Roman Britain. Both have a tendency to silence the voices of the Britons. And so we still have historians who believe that Britain was nothing until the Romans came, and then collapsed into nothingness again until the Church got a grip in the sixth and seventh centuries. What the average Briton actually thought, felt and believed is irrelevant - all that matters is that we celebrate the triumph of institutions (the Roman Empire, the Church of Rome) at the expense of the people.
So where does that leave us today? Is Michael Wood right to see the Fall of the Roman Empire echoed in Europe's contemporary crises?
Let us first of all remember that trade existed between Britain and Continental Europe before the Romans marched into the land and imposed their own ideas on the Britons. Maybe Julius Caesar had been right when he argued that Druidism - not so much a 'religion' as an intellectual system and a repository of knowledge - originated in Britain. There are those who like to believe that the Romans stamped out Druidism when they destroyed a major college on Anglesey in AD 60, but that view is profoundly unrealistic. Why should a centuries-old system of learning and wisdom vanish just because it was told to?
If there is a contemporary European parallel with the post-Roman Britain of Arthur's time, it is perhaps the appalling effect of 'Anglo-Saxon' economics, a kind of slash-and-burn policy which benefits the greedy. This proved as attractive to certain individuals, mostly in the south and east of Britain, as the advent of Roman rule did nearly 2,000 years ago. It offered a get-rich-quick opportunity, and the price we're paying is the destruction of local services (a phenomenon which, according to Michael Wood, matches the situation in post-Roman Britain).
The emergence of Scottish independence as a political issue in recent times is another reminder of the original Arthur, the son of the King of the Scots. Arthur son of Aedan was born exactly 150 years after the departure of the last Roman legion, and at the very moment when the Germanic settlers were launching their conquest of North Britain. By his example, he showed how the Britons could unite with their Celtic allies to mount a counterattack that, until it was brought down by treachery, proved remarkably successful.
The south had fallen, first of all to the attractions of Roman luxury, and then to the consequences of 'Anglo-Saxon' economics. But the North held out, true to its traditions. The problem, when it came, took the form of religious fundamentalism.
If we want to prevent the complete collapse of Britain - as happened in the immediate aftermath of Artuir mac Aedain's death in 594 - then we have to guard against the rise of religious intolerance and its attendant right-wing politics. That was what destroyed Britain the first time around. The apparent collapse of the European dream - symbolised by the Treaty of Rome - is not what will cause Britain's demise. It is the (southern) love affair with easy money, and the consequent imposition of Germanic austerity, that has caused the problem which we now face. Hard times lead to strange beliefs, and all it will take is the appearance of an ambitious and unscrupulous 'prophet' to plunge Britain back into the Dark Ages.
That's what happened in Arthur's day, and it could happen again. But now, as then, the Scots (whose land includes much of what was British territory in Arthur's day) might be able to show us the way.
By remaining true to themselves, the Scots have been able to grow their economy (they currently contribute almost twice as much to the British Treasury as they get back in services), while England's economy is contracting, thanks to the southern fondness for Roman-style luxury and, latterly, the Germanic obsession with austerity. There is, then, a Light in the North, very much as there was in Arthur's day. What might snuff it out is religious fanaticism, selfishness, paranoia and intolerance. Maybe even a figure like Donald Trump.