IT was a day a Roman legionary would have longed for: hot as a skillet, with a cloudless sky the colour of the Mediterranean under brilliant sun. On Hadrian’s Wall, once the most far-flung frontier of the Roman Empire, you more usually find weather that fits a southerner’s idea of the north. Wind, rain, sleet and biting cold come as standard out here on the Northumberland moors. No doubt such conditions helped cement the idea that those who lived beyond were primitive.

Last week’s summer blaze, however, was a reminder of the origins of probably the most remarkable empire ever known. Forged in ancient Rome, this vast territory was the vision of a succession of rapacious rulers, for whom the word ‘ego’ barely hints at their all-consuming self-interest and ambition.

To sit in a café in the Campo de’ Fiore and think of subjugating all the land between there and the Orkneys – in a time when horses were the fastest mode of transport, and most armies travelled on foot – is to catch a glimpse of the overweening confidence and strength of Rome and its followers.

More staggering still is to stand and survey, as I did in my sun-hat a few days ago, the remains of the fort of Vindolanda. Close to Hadrian’s Wall, this was a magnificent and sophisticated settlement, which predates the building of the Wall. It is astonishing testimony – as are what remains of the Wall – to human resilience, determination and the lust for power.

Looking from Vindolanda across the scrub and woodland that fade into the distance towards Scotland, you can see where the author GRR Martin got his inspiration for the fearsome wall of ice in Game of Thrones. As he discovered when he visited, a vertiginous, well-guarded barrier designed to keep terrifying barbarians in check, is a potent image. So too the viperish infighting of those in charge of the empire, who were so treacherous assassins lurked around every corner.

With Game of Thrones’s prequel House of the Dragon beginning on HBO later this week, Hadrian’s Wall is once again in the limelight, even if most viewers don’t realise it. The series’ popularity might briefly have helped boost visitor numbers along the Wall, but reasons to seek out evidence of the Roman occupation are compelling enough without any fictional lure.

Looking at the wealth of materials and objects left by the invaders who spent several lifetimes in the north of England, it is difficult to believe this occupation ever really happened. The site at Vindolanda is remarkable, its purpose so preposterous it would not be surprising to learn it had simply fallen out of the sky.

That the Roman Empire stamped its image on such a remote area almost 2000 years ago feels more like a dream than reality. That sense of awe and incredulity is heightened in the Vindolanda museum, which is stuffed with shoes, jewellery, cooking pots, weapons, tools and, most sensationally, fragments of letters.

Each object speaks to thousands of individual lives spent in an outpost eerily distant from home, wherever in the empire that might have been. There were of course those, as described in Rosemary Sutcliff’s brilliant The Eagle of the Ninth and its sequels, who found everything they needed here, and hoped never to be recalled to Rome.

The story of the Romans in Scotland is another matter entirely, although it’s worth noting that soldiers from Trimontium, the large cavalry fort at Newstead near Melrose, helped to build and supply Hadrian’s Wall.

The atmosphere around the crumbling Northumbrian ramparts is sobering. Ancient history though this is, the ideas behind its construction and what it was intended to represent are still very familiar to us today, and not only if you live on the Mexican border.

The concept of empire and its legacy is one with which the UK is only belatedly beginning to grapple. But even if its impact continues to reverberate centuries and decades later, that particular international stranglehold is now largely a thing of the past.

Not so elsewhere, as leaders across the globe still aspire to the Roman model, knowingly or not. Despite history showing that over-reaching one’s national sphere of influence and authority always, ultimately, fails, each new despot thinks they will prevail.

There is something forlorn about the traces that remain of the Romans in Scotland and the north of England. They represent a massive, impressive and misguided expenditure of energy and intelligence. In the scale of the enterprise at Vindolanda and its neighbouring forts, you see a ferocious world view that depended on possession and subjugation.

Under such a regime nobody, not even the wealthiest in Rome, could live at ease. Knowing what the state was capable of doing to others, everybody knew it could treat its own citizens atrociously as circumstances demanded.

It is unlikely that today’s empire-builders ever give a thought to the likes of Hadrian or Septimius Severus, as they galvanised their troops and gloated at the sight of their territories creeping over much of the map.

Does Putin see parallels in his annexing of Crimea and his invasion of Ukraine with Rome’s bloody heyday? Does Xi Jinping reflect on the resistance put up by Celtic tribes as Taiwan starts to prepare itself for conflict, or the Japanese increase their patrol of the South China Sea, which China dearly wishes to control?

Back home, the imperial mindset lives on among those who viewed Brexit as a return to the glory days of dominion over our own inviolable borders. As it does with a leader such as Boris Johnson who, like emperors of old, is eager to bolster his personal legacy before he waltzes off to the speaking circuit.

One suspects that he can think of nothing more fitting than a coin minted with his head upon it, complete with laurel wreath.

Those who would build empires should visit Hadrian’s Wall, and see what came of that breath-taking venture. W H Auden captured the inevitable reversal of fortunes in ‘The Fall of Rome’: “Caesar’s double-bed is warm/As an unimportant clerk/ Writes I DO NOT LIKE MY WORK/ On a pink official form.”

Written in 1947, this is as much about the retreat of the British Empire after partition in India, as the doings of Caesar and his henchmen. In the end, as Auden recognised, all empires crumble. As do walls.