Once upon a time? Yes, well once upon a time the Portsmouth area was just one tiny part of a gaseous and extremely hot ball, spinning around the sun at a fair old lick - but then that's not the "once upon a time" that we're after, is it.
Rather, we need to come forward to a time when people first started appearing in the area, but just briefly, we should pause as we pass through the cretaceous era, which ended about 65 million years ago and gave way to the cenozoic era, which we're still in now, as it happens.
Most of the rock beneath southern Hampshire and the Isle of Wight was formed during that earlier geological area - cretaceous clays, the geologists call the soil, which break down into a variety of top soils, but a quick peek at a geological map for the area shows that there is also a lot of chalk, which runs across an area including Portsdown Hill and the northern bit of Portsea Island.
Should I care about that, do I hear you ask? Well, maybe not, except that all that chalk has played quite an important role in the development of Portsmouth, partly because the action of the sea on it helped create the large natural harbour that was really responsible for the creation and expansion of the city.
It also goes a good bit further than that, because the Portsmouth in the centuries before the Romans came to Britain - or rather, the island on which Portsmouth would eventually be built, was a lot different to the island that we know today - and not just for the more obvious reasons, in that there were no high rise buildings and so on.
No, the Portsea Island of, say, 500BC - and even in the ensuing millennium, right up to the time of the Norman conquest - was a pretty boggy old place, with a good portion of the land below sea level and prone to regular flooding and dotted with permanent marshes.
As a result, the land around what we now know as Portchester was much more attractive to potential settlers and farmers of the time and, although the early history of this area is not known in any certain detail, the village at Portchester was almost certainly the "trigger" for the eventual growth of Portsmouth.
What we do know about Portchester comes from a chronicle written by Higden, the Monk of Chester, who wrote that two sons of an ancient British king, Peres and his elder brother Ferrex, fought for the crown after their father's death and Ferrex was killed.
Peres then built what he named Caer-Peris, which was the name by which Portchester was known to the Britons. The first reference to the area as any sort of naval station came in 286AD, when Rome sent a sea captain named Carausius to sort out the growing piracy problem.
Carausius in turn became a master pirate, but he then went too far, assuming Imperial power and even minting his own coinage, but this was too much for his masters in Rome, who despatched a massive force to crush this rebellion.
Having achieved this, the powers-that-were quickly realised the commanding position offered at Portchester and set about fortifying it and developing it as a naval centre, changing its name to Portus Adurni.
Accounts of Portchester's development after the Romans are patchy, but we do know that in 897AD Alfred the Great gathered a large fleet in the Solent - probably using Portchester as his "landing stage" - and achieved a great victory over the Danes and went on to capture twenty of their ships, later in the same year.
The writing was already on the wall as far as taking advantage of Portsmouth Harbour as a naval base, but it would be a few more years before that aspect of the area was fully exploited.
Meanwhile, Saxon farmers had established a handful of tiny settlements on Portsea Island, the majority no more than a farmhouse and perhaps a barn or two, although, by the time of the Normans, there were three notable hamlets, Buckland, Copenore (Copnor) and Froddington (which eventually became known as Fratton).
These hamlets and the odd farmsteads were situated on the areas of higher ground across the island and during the winter months and after the various seasonal high tides, travelling between these areas could be a very sticky business indeed and often what passed as roadways were impassable to wheeled traffic for weeks on end.
Fortunately, our ancestors were hardy souls and the chalk that was readily available nearby, was easy to quarry and use to build up trackways. Clay from the same chalk was also employed, to help raise soil levels, but clay is not an ideal growing medium and hauling tons of chalk and clay in rudimentary carts was no fun!
However, an area of land the size of Portsea Island was never going to be ignored permanently and its position was superb, from the point of view of maritime trading and, as we already know, there was already a "role model" close by, to show exactly what might be possible.
Just across the harbour from Portsea Island still lay the village and castle at Portchester, the latter founded by the Romans and, as we've already said, the first recorded settlement of any size in the whole area, but that was now about to change.
The Normans had been masters of England for 120 years or so and, after initial Saxon rebellions, managed to establish a degree of peace, partly by building some impressive castles, initially from timber and then from stone and installing loyal Norman lords, together with well trained garrisons.
Portchester Castle was an ideal target for such an enterprise - the outer Roman "curtain" wall, built of flint and mortar, already defended a sizeable area and all it needed was a bit of Norman architecture and that started in 1120, when Henry I ordered the construction of a more modern castle within the Roman walls.
The building work progressed with remarkable speed and although Henry's castle was further added to and improved over the ensuing centuries, the Norman additions were certainly designed to impress the locals and any ships' captains who might sail into the harbour, either for trade, or simply for shelter from the weather.
The original keep and inner bailey were formidable structures and the presence of such a statement of Norman authority not only ensured a degree of security, but also must have instilled a feeling of greater confidence among would-be Norman entrepreneurs.
It didn't happen immediately after the Conquest, for there is no mention of Portsmouth in the Domesday Book - although Buckland, Froddington and Copenore were deemed worthy of a few lines. What was needed was someone with the money and enterprise to grab the sort of opportunity that doesn't appear often throughout history and, a century or so after the Domesday survey, along came such a man.
The year was 1180 - and enter one Norman noble by the name of Jean de Gisors, a knight, landowner and merchant, with a fair bit of money, some of which he used to buy the Buckland settlement and estate from the de Port family, which is most likely why Jean decided to name his new "town" Portsmouth, although some historians still think it may have been simply because the town stood at the mouth of what he knew would become the foremost port for many miles around.
Whatever the truth behind the name, the important fact is that Jean was not a man for slapdash half measures and he carefully put together a grid system, which would govern how and where the buildings of Portsmouth would be erected.
The Romans knew the worth of such town planning, when and where they were able to institute it, but the towns that had grown up since the fourth century had simply "spread", without too much thought to aesthetics.
Take a look at a map of Old Portsmouth (albeit a map from long after Jean de Gisors' day) and compare it with a map of the rest of the city and see the difference!
Although almost all the original 12th and 13th century buildings were destroyed by French raiders, who attacked the town on several occasions, the replacement building continued to follow the original layout and the map on the right demonstrates how neatly the town was planned - the map below that shows how later builders failed to carry on the same idea.
In the early 1180s, however, those early inhabitants of Portsmouth would not have known how crudely the French would treat their building efforts, nor that records of their contributions to the birth of what would eventually develop into one of the most famous cities in the world would largely end up in smoke and ashes.
What little we do know about those first years of the new town is contained in the Southwick Cartularies, an early 13th century document, listing the richest people in the country, and especially the southern region, together with details of their lands, which was compiled and kept by the monks at Southwick Priory, which thankfully lay far enough inland to escape the attentions of the French raiders.
(Southwick Priory was once thought to have been founded in 1133, by Henry I, but more recent research appears to confirm that it was actually founded four or five years earlier, by one William de Pont de l'Arche, Sheriff of Hampshire, Wiltshire and Berkshire.).
French or no French - and their attacks were still very much in the future - Jean de Gisors had cast the die for Portsmouth and he was a man who knew how to get things done and get to the top. In 1186 he gifted a parcel of land to Southwick Priory for the erection of a new chapel and, whatever his motives might have been, there can be little doubt that such a pious act would stand him in good stead in the highest circles.
Sure enough, on 2 May 1194, the people of Portsmouth received their first royal charter, possibly from the king himself, for Richard I was in the harbour at the time, with a fleet of more than one hundred ships, aboard which was a great army, waiting for the weather to improve sufficiently to cross the Channel to Normandy.
Already Portsmouth and its harbour were proving their worth and, in the next century or so, great developments awaited ...