Today is the 1900th anniversary of a seminal moment in Scottish history, except that nobody knew it at the time and very few people will realise the significance of the event even now.

For it was on 10 August, 117, that Publius Aelius Hadrianus (later adding the names Caesar, Traianus and Augustus) became the Emperor of Rome.

We know him better as Hadrian, builder of the eponymous Wall that more or less defined the southern edge of Scotland from his reign onwards, and definitely made most of the tribes of Scotland outwith both the Roman Empire and the kingdoms that merged centuries later to become England.

In short, it is thanks to Hadrian’s Wall that the land which became Scotland was first considered one territory.

It’s also a fact that we know more about Hadrian than just about every King of the Scots until Malcolm Canmore who reigned almost 1000 years later, and the emperor who in a real sense created Scotland turned out to be a fascinating character.

WHO WAS HE?

Hadrian is known as one of the Five Good Emperors, the others being Nerva, Trajan, Antoninus Pius and Marcus Aurelius.

Trajan immediately preceded Hadrian and ruled over Rome from 89 to 117, greatly expanding the empire and building many important works in the city itself, including the Trajan Forum, the remains of which can be seen to this day.

Hadrian’s family were from modern-day Spain and he may have been born there or in Rome in 76, as his father was the cousin of Trajan, who looked after the boy when Hadrian’s father died when the future emperor was just nine.

Groomed to be at least a senator like his father from his early years, Hadrian entered military service and his family connections and undoubted soldierly skills saw him advance rapidly in society, serving as tribune for three legions. The Emperor Nerva singled out Hadrian for the honour of informing Trajan that he was being officially adopted as heir, and Trajan’s family – especially his wife Plotina – gave their support to Hadrian ever afterwards. Indeed, he married the emperor’s grand-niece Vivia Sabina, and soared through the high offices of Rome to become consul in 108.

Things changed in Rome, however, and though Trajan continued to respect Hadrian, political conspiracies saw him sent to Greece, much to Hadrian’s delight as he was a lover of all things Hellenic. He also had a lifelong curiosity about almost every subject under the sun, including philosophy, engineering and architecture, as we shall see.

When the Parthian wars began near the end of Trajan’s life, it was Hadrian as commander in Syria who became his chief general, for the clever and experienced Hadriantruly was the best officer in the Roman Army. Shortly before he died, Trajan adopted Hadrian and named him his successor.

A day or so after Trajan’s death, the Roman Army proclaimed 41-year-old Hadrian as the new emperor, and his reign was under way.

WHY A WALL?

Hadrian knew the east of the empire well, but not the far west. He travelled through Gaul to Britain in 121/122 and there he was told of the fierce barbarians to the north, so often portrayed on page and screen as savage Celts, who frequently raided south deep into Roman Britain.

These “barbarians” were most likely the Picts who then occupied most of what is now Scotland.

As someone who commissioned or oversaw the building of bridges, aqueducts and temples and who made the Pantheon the greatest building in Rome – it survives largely intact even now – the solution to the northern problem was simple. He would keep out the barbarians, and thus ordered the construction of a wall right across the “waist” of Britain from Luguvalium to Coria, or Carlisle to Corbridge as we know them.

The story is told that he was informed that it couldn’t be done – Hadrian went to Eboracum (York) and supposedly drew up the first plans himself.

For the first time, the inhabitants of what we know as Scotland knew they had a southern limit – not that it stopped them invading anyway. It was 73 miles long and in places was up to 12 ft high and 20ft wide, with forts and fortlets spread out along the wall. It remains the largest Roman artefact still extant in the world.

WAS IT REALLY THE FIRST SOUTHERN BORDER OF SCOTLAND?

Never officially called the border, the Wall still marked the extent of the Roman Empire with everything south being Roman Britain, especially after the Antonine Wall between the Clyde and Forth was abandoned only eight years after it was completed in 154. And the Romans did not leave until the 5th century.

So for centuries, everything north of Hadrian’s Wall was seen as the land of the barbarians, and that is why, when the land we know as England was invaded by the Angles, Saxon, Jutes, Danes and Norsemen, the peoples north of the Wall were left to their own devices.

SO THE ROMANS NEVER REALLY CONQUERED US?

It has been argued that no one has ever really “conquered” Scotland in that the country we think of as Scotland did not really come into being until the Picts and Scots joined together and later took back Strathclyde and the Lothians from the Britons and the Northumbrians respectively – it was only in 1018 that the Battle of Carham finally confirmed the land north of the Tweed on the east coast as part of Scotland. Various English kings claimed “overlordship” of Scotland, but the man who came closest to conquering this land was a commoner, Oliver Cromwell, and even he left alone the far north and the Hebridean islands.

Hadrian died in 138, having defined the limits of the Roman Empire in the West, limits that did not include Scotland, and we should be grateful to him, for it took a man of genius to realise that the people of this land are different from those south of his Wall.