The Treaty of Alfred and Guthrum, preserved in Old English in Corpus Christi College, Cambridge ( Manuscript 383 ), and in a Latin compilation known as Quadripartitus, was negotiated later, perhaps in 879 or 880, when King Ceolwulf II of Mercia was deposed.

For Bede, Mercia was a traditional enemy of his native Northumbria and he regarded powerful kings such as the pagan Penda as standing in the way of the Christian conversion of the Anglo-Saxons.

Their next target was Mercia where King Burgred, aided by his brother-in-law King Æthelred of Wessex, drove them off.

Æthelflæd had been negotiating with the Northumbrians to obtain their submission, but her death put an end to this and her successor, her brother Edward the Elder, was occupied with securing control of Mercia.

" The investigations at Bristol, applying isotope tests on tooth enamel, checked whether she was born and brought up in Wessex and Mercia, as written history has indicated.

The kingdom was bounded to the north by the River Stour and the Kingdom of East Anglia, to the south by the River Thames and Kent, to the east lay the North Sea and to the west Mercia.

For most of the kingdom's existence, the Essex king was subservient to an overlord-variously the kings of Kent, Anglia or Mercia.

This rebellion was suppressed by Wulfhere of Mercia who established himself as overlord.

However, by the mid 8th century much of the kingdom, including London, had fallen to Mercia and the rump of Essex, roughly the modern county, was now subordinate to the same.

Succession crises meant Northumbrian hegemony was not constant, and Mercia remained a very powerful kingdom, especially under Penda.

By the end of Alfred's reign in 899 he was the only remaining English king, having reduced Mercia to a dependency of Wessex, governed by his son-in-law Ealdorman Aethelred.

Edward, and his brother-in-law Æthelred of ( what was left of ) Mercia, began a programme of expansion, building forts and towns on an Alfredian model.

Another abbey was founded by King Offa of Mercia in 793.

But before the Law of the Normans was the Law of the Danes, The Danelaw had a similar boundary to that of Mercia but had a population of Free Peasantry which were known to have resisted the Norman occupation.

The South Saxons were first evangelised extensively under Anglian influence ; Aethelwalh of Sussex was converted by Wulfhere, King of Mercia, and allowed Wilfrid, Archbishop of York, to evangelise his people beginning in 681.

Suffolk, and several adjacent areas, became the kingdom of East Anglia, which was settled by the Angles in the 5th century AD, later merging with Mercia and then Wessex.

After Cadwallon ap Cadfn, the king of Gwynedd, in alliance with the pagan Penda of Mercia, killed Edwin of Deira in battle at Hatfield Chase in 633 ( or 632, depending on when the years used by Bede are considered to have begun ), Northumbria was split between its constituent kingdoms of Bernicia and Deira.

Æthelflæd, daughter of Alfred the Great, and her husband Æthelred, ealdorman of Mercia, were buried in the priory, and their nephew, King Æthelstan, was a major patron of Oswald's cult.

The fortunes of the kingdom were transformed when Egbert conquered part of Dumnonia, seized control of Surrey, Sussex, Kent and Essex, conquered Mercia and secured the overlordship of the Northumbrian king, although Mercian independence was restored in 830.

Cynegils's godfather was King Oswald of Northumbria and his conversion may have been connected with an alliance against King Penda of Mercia, who had previously attacked Wessex.

During the 8th century Wessex was overshadowed by Mercia, whose power was then at its height, and the West Saxon kings may at times have acknowledged Mercian overlordship.

The Danish conquests had destroyed the kingdoms of Northumbria and East Anglia and divided Mercia in half, with the Danes settling in the north-east while the south-west was left to the English king Ceolwulf, allegedly a Danish puppet.

They withdrew to Mercia, but, in January 878, made a sudden attack on Chippenham, a royal stronghold in which Alfred had been staying over Christmas, " and most of the people they killed, except the King Alfred, and he with a little band made his way by wood and swamp, and after Easter he made a fort at Athelney in the marshes of Somerset, and from that fort kept fighting against the foe ".

It entailed the recruitment of clerical scholars from Mercia, Wales and abroad to enhance the tenor of the court and of the episcopacy ; the establishment of a court school to educate his own children, the sons of his nobles, and intellectually promising boys of lesser birth ; an attempt to require literacy in those who held offices of authority ; a series of translations into the vernacular of Latin works the king deemed " most necessary for all men to know "; the compilation of a chronicle detailing the rise of Alfred's kingdom and house ; and the issuance of a law code that presented the West Saxons as a new people of Israel and their king as a just and divinely inspired law-giver.

The rulers of Mercia were generally the most powerful of the Anglo-Saxon kings from the mid-7th to the early 9th centuries, but are not accorded the title of bretwalda by the Chronicle, which is generally thought to be because of the anti-Mercian bias of the Chroniclers.

This battle marked a major turning point in Northumbrian fortunes: Penda died in the battle, and Oswiu gained supremacy over Mercia, making himself the most powerful king in England.

The most credible source for the conceit of a contemporary Mercia is Thomas Hardy ’ s Wessex novels.

She was an ally of her husband's most trusted adviser, the deeply distrusted Eadric Streona, ealdorman of Mercia, and he took her side, but she was opposed by Æthelred's oldest surviving son, Edmund Ironside, and his allies, who naturally regarded him as the heir.

Gwynedd was the most powerful of these kingdoms in the 6th century and 7th century, under rulers such as Maelgwn Gwynedd ( died 547 ) and Cadwallon ap Cadfan ( died 634 / 5 ) who in alliance with Penda of Mercia was able to lead his armies as far as Northumbria and control it for a period.

Æthelbald, who ruled Mercia for most of the forty years before Offa, was also descended from Eowa according to the genealogies: Offa's grandfather, Eanwulf, was Æthelbald's second cousin.

During a sustained campaign of repeated attack between 865 and 878 the Danish Vikings overran most of the English Kingdoms such as Northumbria, Eastern Mercia, East Anglia and even threatened the very existence of Wessex.

The new regime thus established was dominated by the most powerful surviving members of the English ruling class, Stigand, Archbishop of Canterbury, Ealdred, Archbishop of York, and the brothers Edwin, Earl of Mercia, and Morcar, Earl of Northumbria.

With the exception of the short reign of Beornrad, who succeeded Æthelbald for less than a year, Mercia was ruled for eighty years by two of the most powerful Anglo-Saxon kings, Æthelbald and Offa.

For most of the eighth century, Mercia was dominant among the Anglo-Saxon kingdoms south of the river Humber.

From about 627 onwards, Edwin was the most powerful king among the Anglo-Saxons, ruling Bernicia, Deira and much of eastern Mercia, the Isle of Man and Anglesey.

Perhaps the most significant legacies of Edwin's reign lay in his failures, the rise of Penda and of Mercia, and the return from Irish exile of the sons of Æthelfrith which tied the kingdom of Northumbria into the Irish sea world for generations.

King Anna of East Anglia married his daughter, Seaxburh, to Eorcenberht, and their daughter Eormenhild married Wulfhere of Mercia, one of the most powerful kings of his day.

Contrary to certain reports, the name has nothing to do with Leofric, an 11th-century Earl of Mercia ( most famous for being the miserly husband of Lady Godiva ).

Stone was the capital of early Mercia, a powerful Anglian kingdom that later expanded over most of what is now the West Midlands.

The late 7th century saw the kingdom of Mercia expand, absorbing the Hwicce by the late 8th century and eventually coming to dominate most of England, but the growth of Viking power in the later 9th century saw eastern Mercia fall to the Danelaw, while the western part, including the Birmingham area, came to be dominated by Wessex.

A daughter of King Penda of Mercia, Edburga was a nun for most of her life.

Although the Vercelli and Exeter manuscripts were primarily late West Saxon in their scribal translations, it is most probable that Cynewulf wrote in the Anglian dialect and it follows that he resided either in the province of Northumbria or Mercia.

During Chad's lifetime the most important conflict was between Northumbria and Mercia.

The most obvious reason for Chad's tortuous travels would be that he was also on a diplomatic mission from Oswiu, seeking to build an encircling alliance around Mercia, which was rapidly recovering from its position of weakness.