Go big or go home

After Roman rule collapsed at the start of the fifth century, everything changed in Britain – politically, socially, culturally and economically. Migration from northern Europe and around the Irish Sea contributed to the development of new kingdoms across the island that competed for power, or just for survival, until the advent of the Vikings marked a watershed at the end of the eighth century. Some of these kingdoms – Wessex in south-west England; Mercia in the Midlands; Northumbria in the north-east; East Anglia; and Gwynedd in north-west Wales – left an enduring legacy. Others sank with barely a trace.

So what factors brought long-term success? Growth was one key strategy. It wasn’t a universal prerequisite – East Anglia, for example, remained largely static in size and shape until the Viking Great Army conquered it in AD 869. But most of the big beasts of early medieval Britain were realms that pursued aggressive, expansionist policies.

Take Northumbria, itself formed from the merger of two smaller kingdoms, Bernicia and Deira. It swallowed up several near neighbours, and had a crack at others. Mercia was the midland realm with perhaps the greatest ambitions of all – particularly during the reign of Offa (ruled 757–796) and his successor Coenwulf (r796–821). In the eighth century, it controlled an empire that extended from the Welsh borders to the Wash and south to the Channel. At its height, Mercia could claim overlordship of Sussex and Kent, Hwicce, Lindsey and parts of Wales.

Wessex, the south-western realm that was later the only survivor of the Viking cataclysm, entered the mid-ninth century in control of all of Britain south of the Thames. Not all of the unsuccessful kingdoms lacked ambition, but all failed to capitalise on it. Some, such as Essex, were unable to press their advantages when they had them – or, as the next section shows, to hold on to their gains when they had made them.

Keep it together

One thing that pretty much guarantees political instability is division over major cultural issues. Being at loggerheads with yourself for a prolonged period of time offers opportunities for malign outside powers to twist the chisel and split the wood.

Take, for example, the kingdom of Essex that coalesced in the late sixth century. On paper, by the early seventh century its people, the East Saxons, had it all. Theirs was a solid chunk of contiguous territory between the Thames and the Stour encompassing the modern counties of Essex and Middlesex and much of Hertfordshire. That included a long stretch of coastline with easy access to continental imports and ideas. They also had some control of the lower Thames and its estuary, and riverine access into the heart of southern Britain.

And they had the walled city of Londinium – largely defunct, true, but still strategically vital and symbolically valuable as the former capital of Roman Britannia. Yet by the ninth century, the East Saxon kingdom was a shadow of its former self. Confined to Essex, its kings were bit players on the political stage, subject to the whims of others and on the verge of losing their independence.

So what went wrong? In a word, religion. The first king we know anything about – Sæberht (reigned c604– c616) – was pressured by his uncle, King Æthelberht of Kent, to convert to Christianity and allow the first church of St Paul’s to be built in London. His three sons were less enthusiastic. On their father’s death, they reverted to pagan ways and sent the bishop, Mellitus, packing. This pattern was repeated more than once: Christianity introduced with the backing of outside kingdoms was overturned by a pagan backlash.

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Tension between Christian and pagan factions persisted, their leaders supported at different times by asymmetrical alliances with more powerful foreign allies: Northumbria, Mercia, East Anglia, Wessex. It was a trend exacerbated by a habit of joint but uncooperative kingship exercised by the East Saxon royal family.

These political fault lines were ripe for exploitation, and the senior partners in these alliances gained ever greater power. The main beneficiaries were the Mercians who, by the mid-eighth century, were effectively in control of London and Middlesex. By the time Essex fell under the sway of Wessex in the ninth century, its kings must have long given up hope of returning to the big league.

The kingdoms of the Dark Ages, c600

East Anglia

Settled by northern European migrants from the fifth century, this kingdom comprising the “northern folk” (Norfolk) and “southern folk” (Suffolk) survived until Vikings invaded in the second half of the ninth century.


Founded in folklore by fifth-century Jutish adventurers Hengist and Horsa, Kent entered history as a Christian kingdom in the late sixth century. By the eighth century it became dominated by Mercia, and was subsequently absorbed into Wessex after 825.


The realm of the East Saxons – at one time spanning what’s now Essex, Middlesex and southern Hertfordshire – was annexed by Wessex in the ninth century.


Probably based originally in the Thames Valley, the kingdom of the Gewissæ shifted to Hampshire and Dorset, rebranding as Wessex. The West Saxons harried Sussex during the seventh and eighth centuries, and in 825 conclusively wrested dominance of southern Britain from Mercia.


This long-lasting kingdom, in what is now Cornwall and Devon, had its origins in the pre-Roman Iron Age but was crushed by Wessex in the ninth century.


From its heartland in the upper west Midlands, Mercia grew to encompass much of central, eastern and southern Britain. During the eighth century, notably under King Offa (r757–796), Mercia controlled Lindsey, East Anglia, Essex, Kent, Hwicce and Sussex, but declined in the ninth century after defeat to Wessex.


The kingdom of Gwynedd was the longest-lasting and most politically important realm of the British west until England finally gained control in the 13th century.


Based on the Iron Age tribal territory of the Demetae, Dyfed was absorbed into the larger realm of Deheubarth in the tenth century, then invaded by the Normans following the Norman Conquest.


The land of the people “north of the Humber” was the product of a seventh-century merger between Deira and Bernicia, and extended as far north as the Firth of Forth. In the mid-860s it was settled and ruled by Vikings until it became part of the kingdom of England in 954.

Dál Riata

This Gaelic-speaking kingdom covered most of Scotland’s Atlantic fringe. It disappeared from history in the mid-ninth century, and parts of its former territory were incorporated into the kingdom of Alba.

Alt Clut

This kingdom was centred on Dumbarton Rock in the Clyde until the fortress there was destroyed in 870. Rebranded as Strathclyde, the kingdom staggered on into the 11th century.

Get religion, keep the faith

Though religion could be the undoing of a kingdom, it could also be instrumental in a realm’s survival. In the early stages of its spread across Britain, Christianity was not essential to the success of a kingdom.

The seventh-century pagan kings Æthelfrith of Northumbria and Penda of Mercia set the stage for the later dominance of their respective kingdoms with exceptionally aggressive careers. Æthelfrith was remembered by the early eighth-century scholar Bede (with some approval, it has to be said) for slaughtering 1,200 monks at the battle of Chester in c613–16. Penda, meanwhile, defeated the army of the saintly King Oswald of Northumbria at the battle of Maserfelth in c642 – then nailed the vanquished leader’s head and severed limbs to wooden stakes. Neither Æthelfrith nor Penda appear to have been held back by their heathenry.

Yet it is also true that no kingdom survived to face the Viking Age with its pagan beliefs intact – and those that held out the longest eventually came to notable grief in one way or another.

The South Saxons (the people of Sussex) kept up pagan practices longer than most. According to Bede, as late as the 660s they were still throwing themselves from cliffs in response to famine – in despair, perhaps, or as an auto-sacrifice to some bloodthirsty deity. When Saint Wilfrid washed up there in the portentous year 666, he is said to have encountered a sorcerer standing “on a high mound like Balaam” [a Biblical prophet], cursing Wilfrid’s crew and “trying to bind their hands with his magical art”.

The enduring paganism of the South Saxons made them vulnerable in a number of ways. First, it provided neighbouring kings (specifically, of Mercia) with a ready-made tool – sponsored baptism with diplomatic strings attached – by which they could formalise their position as overlords. Second, it opened the door to missionaries from elsewhere who could seed cultural – and, subsequently, political – influence at court and in the wider populace. In this way, older values and traditions were progressively overwritten until they were forgotten.

Third, failure to adopt Christianity on their own terms denied to the South Saxons the vital technology of remembering – writing – that might have helped to preserve and foster a sense of idiosyncrasy and communal solidarity in the face of outside pressures. As it was, however, whatever it was that made the South Saxons unique was lost through their conversion by outsiders. Almost all of the known history of the kingdom of Sussex is preserved only in the biography of a Northumbrian missionary, Wilfrid, and the second-hand testimony of a West Saxon bishop, Daniel of Winchester.

Facsimile copy of the Lindisfarne Gospels, which was created in the early eighth century (Photo by travelib history / Alamy Stock Photo)
Facsimile copy of the Lindisfarne Gospels, which was created in the early eighth century (Photo by travelib history / Alamy Stock Photo)

Don’t forget where you came from (but if you do, make something up)

Everyone needs to feel like they belong in some way, and the sense of a shared heritage and common values can be a potent means for communities to feel confident and empowered. It can also provide an ambitious ruler with a compelling means of mobilising people in pursuit of some goal or other. At the same time, it can offer kings the sort of glamorous backstory that emphasises a right to rule, inherited qualities and the imprimatur of deep-rooted tradition.

Most of the nascent kingdoms of early medieval Britain understood this. It underpinned the endemic habit, prevalent until the seventh century, of burying the dead in the environs of (or sometimes inside) the monuments raised by prehistoric people millennia-dead. It’s also the reason for the production of royal genealogies peopled with the gods and heroes of a mythical age – a trend that lasted much longer.

The sense of a shared heritage and common values can be a potent means for communities to feel confident and empowered

One very physical example of how this was utilised is the Pillar of Eliseg, a large stone memorial raised on top of a Bronze Age cairn by the rulers of Powys in the early ninth century. The pillar (which still stands, north of Llangollen) was erected specifically to emphasise the contemporary achievements of King Cyngen. Importantly, it also compared them to those of his great-grandfather Eliseg and an impressive cast of heroic ancestors including the Roman emperor Magnus Maximus and the famous British warlord Vortigern.

It didn’t do Powys much good in the long run: the kingdom vanished for centuries as an independent realm after Cyngen’s death in 854 or 855. However, it was clearly thought essential, probably because his family were relative newcomers to the Powysian throne. At least it meant that he and his kin were remembered. The same wasn’t true of all other kings and kingdoms of the age.

The fifth-century British warlord Vortigern (left) in a 14th-century illustration. Vortigern’s reputation would later be used by King Cyngen of Powys to consolidate his rule (Photo by British Library Board. All Rights Reserved / Bridgeman Images)
The fifth-century British warlord Vortigern (left) in a 14th-century illustration. Vortigern’s reputation would later be used by King Cyngen of Powys to consolidate his rule (Photo by British Library Board. All Rights Reserved / Bridgeman Images)

Write it down…

There are many realms about which very little is known. Then there are those about which nothing is known beyond a name – otherwise obscure tribes such as the Sweordora and the Unecungaga, for example. And there are the unknown unknowns: the kingdoms that we don’t even know that we don’t know about. The factor that makes the difference is the survival of the written word.

In British history, the period from c400 to c800 is not distinguished by the quantity or the reliability of its surviving written sources. No contemporary written texts survive at all for large areas of the island, over very long periods of time. Those that do survive have particular regional and ethnic biases or are largely products of a later period. Bede’s Ecclesiastical History of the English People (c731), for example, is a history framed deliberately to the advantage of English-speaking communities, Roman forms of Christianity and Bede’s own kingdom of Northumbria.

The Anglo-Saxon Chronicle assumed its original form in the 890s at the court of Alfred the Great, king of Wessex. At the time of its creation it represented a sophisticated tissue of favourable reportage, propaganda and tendentious lore designed to bolster the reputation and ambitions of the West Saxon royal dynasty. In this respect, it did a remarkably thorough job. Likewise, the early ninth-century Historia Brittonum was compiled to the benefit of the kings of Gwynedd.

There is, it must be admitted, a certain circularity here: the most successful kingdoms survived the longest, and the longest lasting were the most likely to produce written chronicles, charters and histories. Those that failed are the most likely to have seen their records lost or destroyed. Still, the point remains: if you don’t want your reign or your kingdom to be forgotten, the key strategy for ensuring a long-lasting legacy is simple: write it down.

...but don’t sign up to anything

Much of what is known about the detailed political history of smaller early medieval kingdoms comes from legal documents. In particular, we learn a lot from the appearance in such records of rulers and churchmen as witnesses to land transactions enacted by the kings of larger realms. Their supporting presence in such contexts demonstrates close political relationships, but it also indicates a subordinate role.

Likewise, there are reports of ceremonies in which a king accepted baptism with a more powerful ruler as “godfather”. For example, Æthelwealh of Sussex was baptised in Mercia in 681, in the presence of King Wulfhere. The deal included an arranged marriage to Eafe of the Hwicce – another small kingdom under Mercian “protection” – and a chunk of territory around the River Meon.

Entering into arrangements like these may have seemed expedient at the time: insecure kings might seek to shore up their own position – perhaps in opposition to a rival internal faction or another predatory neighbour. And by accepting a degree of subordination to an “overking”, a smaller realm could gain a great deal of diplomatic leverage and military advantage; this happened repeatedly in Essex.

But the longer-term implications of such deals were rarely positive. Consider the kings of Hwicce. Osric, the first to appear (in charters of the late-seventh century) was styled unambiguously as rex – full king. However, in similar circumstances his successors suffered a demotion, appearing as subreguli – the slightly humiliating “under-kinglets” – or as comites (“counts” – literally, “companions”). One of the last kings of that realm, Uhtred, was afforded by King Offa of Mercia a grudging and limited “degree of rule over his own people”. He was the last to be granted even that.

By the ninth century, Hwicce had entirely lost its independence – not through war and conquest but through bureaucracy. Like many smaller kingdoms, Hwicce was managed out of existence.

Thomas Williams is a historian of the early Middle Ages and a former curator at the British Museum. His latest book is Lost Realms: Histories of Britain from the Romans to the Vikings (William Collins, 2022)


This article was first published in the October 2022 issue of BBC History Magazine