Offa of Mercia Offa was the King of Mercia from 757 until his death in July 796 . The son of Thingfrith and a descendant of Eowa , Offa came to the throne after a period of civil war following the assassination of Æthelbald after defeating the other claimant Beornred . In the early years of Offa ' s reign , it is likely that he consolidated his control of midland peoples such as the Hwicce and the Magonsæte . Taking advantage of instability in the kingdom of Kent to establish himself as overlord , Offa was also in control of Sussex by 771 , though his authority did not remain unchallenged in either territory . In the 780s he extended Mercian supremacy over most of southern England , allying with Beorhtric of Wessex , who married Offa ' s daughter Eadburh , and regained complete control of the southeast . He also became the overlord of East Anglia and had King Æthelberht II of East Anglia beheaded in 794 , perhaps for rebelling against him . Offa was a Christian king who came into conflict with the Church , particularly with Jaenberht , the Archbishop of Canterbury . Offa managed to persuade Pope Adrian I to divide the archdiocese of Canterbury in two , creating a new archdiocese of Lichfield . This reduction in the power of Canterbury may have been motivated by Offa ' s desire to have an archbishop consecrate his son Ecgfrith of Mercia as king , since it is possible Jaenberht refused to perform the ceremony , which took place in 787 . Offa had a dispute with the Bishop of Worcester , which was settled in the Council of Brentford in 781 . Many surviving coins from Offa ' s reign carry elegant depictions of him , and the artistic quality of these images exceeds that of the contemporary Frankish coinage . Some of his coins carry images of his wife , Cynethryth — the only Anglo - Saxon queen ever depicted on a coin . Only three gold coins of Offa ' s have survived : one is a copy of an Abbasid dinar of 774 and carries Arabic text on one side , with " Offa Rex " on the other side . The gold coins are of uncertain use but may have been struck to be used as alms or for gifts to Rome . Many historians regard Offa as the most powerful Anglo - Saxon king before Alfred the Great . His dominance never extended to Northumbria , though he gave his daughter Ælfflæd in marriage to the Northumbrian king Æthelred I in 792 . His reign was once seen by historians as part of a process leading to a unified England , but this is no longer the majority view . In the words of a recent historian : " Offa was driven by a lust for power , not a vision of English unity ; and what he left was a reputation , not a legacy . " Offa died in 796 and was succeeded by his son , Ecgfrith , who reigned for less than five months before Coenwulf of Mercia became king . Background and sources . In the first half of the eighth century , the dominant Anglo - Saxon ruler was King Æthelbald of Mercia , who by 731 had become the overlord of all the provinces south of the river Humber . Æthelbald was one of a number of strong Mercian kings who ruled from the mid - seventh century to the early ninth , and it was not until the reign of Egbert of Wessex in the ninth century that Mercian power began to wane . The power and prestige that Offa attained made him one of the most significant rulers in Early Medieval Britain , though no contemporary biography of him survives . A key source for the period is the " Anglo - Saxon Chronicle " , a collection of annals in Old English narrating the history of the Anglo - Saxons . The " Chronicle " was a West Saxon production , however , and is sometimes thought to be biased in favour of Wessex ; hence it may not accurately convey the extent of power achieved by Offa , a Mercian . That power can be seen at work in charters dating from Offa ' s reign . Charters were documents which granted land to followers or to churchmen and were witnessed by the kings who had the authority to grant the land . A charter might record the names of both a subject king and his overlord on the witness list appended to the grant . Such a witness list can be seen on the Ismere Diploma , for example , where Æthelric , son of king Oshere of the Hwicce , is described as a " " subregulus " " , or subking , of Æthelbald ' s . The eighth - century monk and chronicler the Venerable Bede wrote a history of the English church called " Historia Ecclesiastica Gentis Anglorum " ; the history only covers events up to 731 , but as one of the major sources for Anglo - Saxon history it provides important background information for Offa ' s reign . Offa ' s Dyke , most of which was probably built in his reign , is a testimony to the extensive resources Offa had at his command and his ability to organise them . Other surviving sources include a problematic document known as the Tribal Hidage , which may provide further evidence of Offa ' s scope as a ruler , though its attribution to his reign is disputed . A significant corpus of letters dates from the period , especially from Alcuin , an English deacon and scholar who spent over a decade at Charlemagne ' s court as one of his chief advisors , and corresponded with kings , nobles and ecclesiastics throughout England . These letters in particular reveal Offa ' s relations with the continent , as does his coinage , which was based on Carolingian examples . Ancestry and family . Offa ' s ancestry is given in the Anglian collection , a set of genealogies that include lines of descent for four Mercian kings . All four lines descend from Pybba , who ruled Mercia early in the seventh century . Offa ' s line descends through Pybba ' s son Eowa and then through three more generations : Osmod , Eanwulf and Offa ' s father , Thingfrith . 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 . Æthelbald granted land to Eanwulf in the territory of the Hwicce , and it is possible that Offa and Æthelbald were from the same branch of the family . In one charter Offa refers to Æthelbald as his kinsman , and Headbert , Æthelbald ' s brother , continued to witness charters after Offa rise to power . Offa ' s wife was Cynethryth , whose ancestry is unknown . The couple had a son , Ecgfrith , and four daughters : Ælfflæd , Eadburh , Æthelburh and Æthelswith . It has been speculated that Æthelburh was the abbess who was a kinswoman of King Ealdred of the Hwicce , but there are other prominent women named Æthelburh during that period . Early reign , the midland territories , and the Middle and East Saxons . Æthelbald , who had ruled Mercia since 716 , was assassinated in 757 . According to a later continuation of Bede ' s " Historia Ecclesiastica " ( written anonymously after Bede ' s death ) the king was " treacherously murdered at night by his own bodyguards , " though the reason why is unrecorded . Æthelbald was initially succeeded by Beornred , about whom little is known . The continuation of Bede comments that Beornred " ruled for a little while , and unhappily " , and adds that " the same year , Offa , having put Beornred to flight , sought to gain the kingdom of the Mercians by bloodshed . " It is possible that Offa did not gain the throne until 758 , however , since a charter of 789 describes Offa as being in the thirty - first year of his reign . The conflict over the succession suggests that Offa needed to re - establish control over Mercia ' s traditional dependencies , such as the Hwicce and the Magonsæte . Charters dating from the first two years of Offa ' s reign show the Hwiccan kings as " reguli " , or kinglets , under his authority ; and it is likely that he was also quick to gain control over the Magonsæte , for whom there is no record of an independent ruler after 740 . Offa was probably able to exert control over the kingdom of Lindsey at an early date , as it appears that the independent dynasty of Lindsey had disappeared by this time . Little is known about the history of the East Saxons during the eighth century , but what evidence there is indicates that both London and Middlesex , which had been part of the kingdom of Essex , were finally brought under Mercian control during the reign of Æthelbald . Both Æthelbald and Offa granted land in Middlesex and London as they wished ; in 767 a charter of Offa ' s disposed of land in Harrow without a local ruler as witness . It is likely that both London and Middlesex were quickly under Offa ' s control at the start of his reign . The East Saxon royal house survived the eighth century , so it is probable that the kingdom of Essex retained its native rulers , but under strong Mercian influence , for most or all of the eighth century . It is unlikely that Offa had significant influence in the early years of his reign outside the traditional Mercian heartland . The overlordship of the southern English which had been exerted by Æthelbald appears to have collapsed during the civil strife over the succession , and it is not until 764 , when evidence emerges of Offa ' s influence in Kent , that Mercian power can be seen expanding again . Kent and Sussex . Offa appears to have exploited an unstable situation in Kent after 762 . Kent had a long tradition of joint kingship , with east and west Kent under separate kings , though one king was typically dominant . Prior to 762 Kent was ruled by Æthelberht II and Eadberht I ; Eadberht ' s son Eardwulf is also recorded as a king . Æthelberht died in 762 , and Eadberht and Eardwulf are last mentioned in that same year . Charters from the next two years mention other kings of Kent , including Sigered , Eanmund and Heahberht . In 764 , Offa granted land at Rochester in his own name , with Heahberht on the witness list as king of Kent . Another king of Kent , Egbert , appears on a charter in 765 along with Heahberht ; the charter was subsequently confirmed by Offa . Offa ' s influence in Kent at this time is clear , and it has been suggested that Heahberht was installed by Offa as his client . There is less agreement among historians on whether Offa had general overlordship of Kent thereafter . He is known to have revoked a charter of Egbert ' s on the grounds that " it was wrong that his thegn should have presumed to give land allotted to him by his lord into the power of another without his witness " , but the date of Egbert ' s original grant is unknown , as is the date of Offa ' s revocation of it . It may be that Offa was the effective overlord of Kent from 764 until at least 776 . The limited evidence for Offa ' s direct involvement in the kingdom between 765 and 776 includes two charters of 774 in which he grants land in Kent ; but there are doubts about their authenticity , so Offa ' s intervention in Kent prior to 776 may have been limited to the years 764 – 765 . The " Anglo - Saxon Chronicle " records that " the Mercians and the inhabitants of Kent fought at Otford " in 776 , but does not give the outcome of the battle . It has traditionally been interpreted as a Mercian victory , but there is no evidence for Offa ' s authority over Kent until 785 : a charter from 784 mentions only a Kentish king named Ealhmund , which may indicate that the Mercians were in fact defeated at Otford . The cause of the conflict is also unknown : if Offa was ruling Kent before 776 , the battle of Otford was probably a rebellion against Mercian control . However , Ealhmund does not appear again in the historical record , and a sequence of charters by Offa from the years 785 – 789 makes his authority clear . During these years he treated Kent " as an ordinary province of the Mercian kingdom " , and his actions have been seen as going beyond the normal relation of overlordship and extending to the annexation of Kent and the elimination of a local royal line . After 785 , in the words of one historian , " Offa was the rival , not the overlord , of Kentish kings " . Mercian control lasted until 796 , the year of Offa ' s death , when Eadberht Praen was temporarily successful in regaining Kentish independence . Ealhmund was probably the father of Egbert of Wessex , and it is possible that Offa ' s interventions in Kent in the mid - 780s are connected to the subsequent exile of Egbert to Francia . The Chronicle claims that when Egbert invaded Kent in 825 , the men of the southeast turned to him " because earlier they were wrongly forced away from his relatives " . This is likely to be an allusion to Ealhmund , and may imply that Ealhmund had a local overlordship of the southeastern kingdoms . If so , Offa ' s intervention was probably intended to gain control of this relationship and take over the dominance of the associated kingdoms . The evidence for Offa ' s involvement in the kingdom of Sussex comes from charters , and as with Kent there is no clear consensus among historians on the course of events . What little evidence survives that bears on Sussex ' s kings indicates that several kings ruled at once , and it may never have formed a single kingdom . It has been argued that Offa ' s authority was recognised early in his reign by local kings in western Sussex , but that eastern Sussex ( the area around Hastings ) submitted to him less readily . Simeon of Durham , a twelfth - century chronicler , records that in 771 Offa defeated " the people of Hastings " , which may record the extension of Offa ' s dominion over the entire kingdom . However , doubts have been expressed about the authenticity of the charters which support this version of events , and it is possible that Offa ' s direct involvement in Sussex was limited to a short period around 770 – 771 . After 772 , there is no further evidence of Mercian involvement in Sussex until c . 790 , and it may be that Offa gained control of Sussex in the late 780s , as he did in Kent . East Anglia , Wessex and Northumbria . In East Anglia , Beonna probably became king in about 758 . Beonna ' s first coinage predates Offa ' s own , and implies independence from Mercia . Subsequent East Anglian history is quite obscure , but in 779 Æthelberht II became king , and was independent long enough to issue coins of his own . In 794 , according to the " Anglo - Saxon Chronicle " , " King Offa ordered King Æthelberht ' s head to be struck off " . Offa minted pennies in East Anglia in the early 790s , so it is likely that Æthelberht rebelled against Offa and was beheaded as a result . Accounts of the event have survived in which Aethelberht is killed through the machinations of Offa ' s wife Cynethryth , but the earliest manuscripts in which these possibly legendary accounts are found date from the eleventh and twelfth centuries , and recent historians do not regard them with confidence . The legend also claims that Æthelberht was killed at Sutton St . Michael and buried four miles ( 6 km ) to the south at Hereford , where his cult flourished , becoming at one time second only to Canterbury as a pilgrimage destination . To the south of Mercia , Cynewulf came to the throne of Wessex in 757 and recovered much of the border territory that Æthelbald had conquered from the West Saxons . Offa won an important victory over Cynewulf at the Battle of Bensington ( in Oxfordshire ) in 779 , reconquering some of the land along the Thames . No indisputably authentic charters from before this date show Cynewulf in Offa ' s entourage , and there is no evidence that Offa ever became Cynewulf ' s overlord . In 786 , after the murder of Cynewulf , Offa may have intervened to place Beorhtric on the West Saxon throne . Even if Offa did not assist Beorhtric ' s claim , it seems likely that Beorhtric to some extent recognised Offa as his overlord shortly thereafter . Offa ' s currency was used across the West Saxon kingdom , and Beorhtric had his own coins minted only after Offa ' s death . In 789 , Beorhtric married Eadburh , a daughter of Offa ; the " Chronicle " records that the two kings combined to exile Egbert to Francia for " three years " , adding that " Beorhtric helped Offa because he had his daughter as his queen " . Some historians believe that the Chronicle ' s " three years " is an error , and should read " thirteen years " , which would mean Egbert ' s exile lasted from 789 to 802 , but this reading is disputed . Eadburh is mentioned by Asser , a ninth - century monk who wrote a biography of Alfred the Great : Asser says that Eadburh had " power throughout almost the entire kingdom " , and that she " began to behave like a tyrant after the manner of her father " . Whatever power she had in Wessex was no doubt connected with her father ' s overlordship . If Offa did not gain the advantage in Wessex until defeating Cynewulf in 779 , it may be that his successes south of the river were a necessary prerequisite to his interventions in the southeast . In this view , Egbert of Kent ' s death in about 784 and Cynewulf ' s death in 786 were the events that allowed Offa to gain control of Kent and bring Beorhtric into his sphere of influence . This version of events also assumes that Offa did not have control of Kent after 764 – 765 , as some historians believe . Offa ' s marital alliances extended to Northumbria when his daughter Ælfflæd married Æthelred I of Northumbria at Catterick in 792 . However , there is no evidence that Northumbria was ever under Mercian control during Offa ' s reign . Wales and Offa ' s Dyke . Offa was frequently in conflict with the various Welsh kingdoms . There was a battle between the Mercians and the Welsh at Hereford in 760 , and Offa is recorded as campaigning against the Welsh in 778 , 784 and 796 in the tenth - century " Annales Cambriae " . The best known relic associated with Offa ' s time is Offa ' s Dyke , a great earthen barrier that runs approximately along the border between England and Wales . It is mentioned by the monk Asser in his biography of Alfred the Great : " a certain vigorous king called Offa . . . had a great dyke built between Wales and Mercia from sea to sea " . The dyke has not been dated by archaeological methods , but most historians find no reason to doubt Asser ' s attribution . Early names for the dyke in both Welsh and English also support the attribution to Offa . Despite Asser ' s comment that the dyke ran " from sea to sea " , it is now thought that the original structure only covered about two - thirds of the length of the border : in the north it ends near Llanfynydd , less than five miles ( 8 km ) from the coast , while in the south it stops at Rushock Hill , near Kington in Herefordshire , less than fifty miles ( 80 km ) from the Bristol Channel . The total length of this section is about sixty - four miles ( 103 km ) . Other earthworks exist along the Welsh border , of which Wat ' s Dyke is one of the largest , but it is not possible to date them relative to each other and so it cannot be determined whether Offa ' s Dyke was a copy of or the inspiration for Wat ' s Dyke . The construction of the dyke suggests that it was built to create an effective barrier and to command views into Wales . This implies that the Mercians who built it were free to choose the best location for the dyke . There are settlements to the west of the dyke that have names that imply they were English by the eighth century , so it may be that in choosing the location of the barrier the Mercians were consciously surrendering some territory to the native Britons . Alternatively it may be that these settlements had already been retaken by the Welsh , implying a defensive role for the barrier . The effort and expense that must have gone into building the dyke are impressive , and suggest that the king who had it built ( whether Offa or someone else ) had considerable resources at his disposal . Other substantial construction projects of a similar date do exist , however , such as Wat ' s Dyke and the Danevirke , in what is now Denmark , as well as such sites as Stonehenge from millennia earlier . The dyke can be regarded in the light of these counterparts as the largest and most recent great construction of the preliterate inhabitants of Britain . Church . Offa ruled as a Christian king , but despite being praised by Charlemagne ' s advisor , Alcuin , for his piety and efforts to " instruct [ his people ] in the precepts of God " , he came into conflict with Jaenberht , the Archbishop of Canterbury . Jaenberht had been a supporter of Egbert II of Kent , which may have led to conflict in the 760s when Offa is known to have intervened in Kent . Offa rescinded grants made to Canterbury by Egbert , and it is also known that Jaenberht claimed the monastery of Cookham , which was in Offa ' s possession . In 786 Pope Adrian I sent papal legates to England to assess the state of the church and provide canons ( ecclesiastical decrees ) for the guidance of the English kings , nobles and clergy . This was the first papal mission to England since Augustine had been sent by Pope Gregory the Great in 597 to convert the Anglo - Saxons . The legates were George , the Bishop of Ostia , and Theophylact , the Bishop of Todi . They visited Canterbury first , and then were received by Offa at his court . Both Offa and Cynewulf , king of the West Saxons , attended a council where the goals of the mission were discussed . George then went to Northumbria , while Theophylact visited Mercia and " parts of Britain " . A report on the mission , sent by the legates to Pope Adrian , gives details of a council held by George in Northumbria , and the canons issued there , but little detail survives of Theophylact ' s mission . After the northern council George returned to the south and another council was held , attended by both Offa and Jaenberht , at which further canons were issued . In 787 , Offa succeeded in reducing the power of Canterbury through the establishment of a rival archdiocese at Lichfield . The issue must have been discussed with the papal legates in 786 , although it is not mentioned in the accounts that have survived . The " Anglo - Saxon Chronicle " reports a " contentious synod " in 787 at Chelsea , which approved the creation of the new archbishopric . It has been suggested that this synod was the same gathering as the second council held by the legates , but historians are divided on this issue . Hygeberht , already Bishop of Lichfield , became the new archdiocese ' s first and only archbishop , and by the end of 788 he received the pallium , a symbol of his authority , from Rome . The new archdiocese included the sees of Worcester , Hereford , Leicester , Lindsey , Dommoc and Elmham ; these were essentially the midland Anglian territories . Canterbury retained the sees in the south and southeast . The few accounts of the creation of the new archbishopric date from after the end of Offa ' s reign . Two versions of the events appear in the form of an exchange of letters between Coenwulf , who became king of Mercia shortly after Offa ' s death , and Pope Leo III , in 798 . Coenwulf asserts in his letter that Offa wanted the new archdiocese created out of enmity for Jaenberht ; but Leo responds that the only reason the papacy agreed to the creation was because of the size of the kingdom of Mercia . Both Coenwulf and Leo had their own reasons for representing the situation as they did : Coenwulf was entreating Leo to make London the sole southern archdiocese , while Leo was concerned to avoid the appearance of complicity with the unworthy motives Coenwulf imputed to Offa . These are therefore partisan comments . However , both the size of Offa ' s territory and his relationship with Jaenberht and Kent are indeed likely to have been factors in Offa ' s request for the creation of the new archdiocese . Coenwulf ' s version has independent support , with a letter from Alcuin to Archbishop Æthelheard giving his opinion that Canterbury ' s archdiocese had been divided " not , as it seems , by reasonable consideration , but by a certain desire for power " . Æthelheard himself later said that the award of a pallium to Lichfield depended on " deception and misleading suggestion " . Another possible reason for the creation of an archbishopric at Lichfield relates to Offa ' s son , Ecgfrith . After Hygeberht became archbishop , he consecrated Ecgfrith as king ; the ceremony took place within a year of Hygeberht ' s elevation . It is possible that Jaenberht refused to perform the ceremony , and that Offa needed an alternative archbishop for that purpose . The ceremony itself is noteworthy for two reasons : it is the first recorded consecration of any English king , and it is unusual in that it asserted Ecgfrith ' s royal status while his father was still alive . Offa would have been aware that Charlemagne ' s sons , Pippin and Louis , had been consecrated as kings by Pope Adrian , and probably wished to emulate the impressive dignity of the Frankish court . Other precedents did exist : Æthelred of Mercia is said to have nominated his son Coenred as king during his lifetime , and Offa may have known of Byzantine examples of royal consecration . Despite the creation of the new archdiocese , Jaenberht retained his position as the senior cleric in the land , with Hygeberht conceding his precedence . When Jaenberht died in 792 , he was replaced by Æthelheard , who was consecrated by Hygeberht , now senior in his turn . Subsequently Æthelheard appears as a witness on charters and presides at synods without Hygeberht , so it appears that Offa continued to respect Canterbury ' s authority . A letter from Pope Adrian to Charlemagne survives which makes reference to Offa , but the date is uncertain ; it may be as early as 784 or as late as 791 . In it Adrian recounts a rumour that had reached him : Offa had reportedly proposed to Charlemagne that Adrian should be deposed , and replaced by a Frankish pope . Adrian disclaims all belief in the rumour , but it is clear it had been a concern to him . The enemies of Offa and Charlemagne , described by Adrian as the source of the rumour , are not named . It is unclear whether this letter is related to the legatine mission of 786 ; if it predates it , then the mission might have been partly one of reconciliation , but the letter might well have been written after the mission . Offa was a generous patron of the church , founding several churches and monasteries , often dedicated to St Peter . Among these was St Albans Abbey , which he probably founded in the early 790s . He also promised a yearly gift of 365 mancus es to Rome ; a mancus was a term of account equivalent to thirty silver pennies , derived from Abbasid gold coins that were circulating in Francia at the time . Control of religious houses was one way in which a ruler of the day could provide for his family , and to this end Offa ensured ( by acquiring papal privileges ) that many of them would remain the property of his wife or children after his death . This policy of treating religious houses as worldly possessions represents a change from the early eighth century , when many charters showed the foundation and endowment of small minsters , rather than the assignment of those lands to laypeople . In the 770s , an abbess named Æthelburh ( who may have been the same person as Offa ' s daughter of that name ) held multiple leases on religious houses in the territory of the Hwicce ; her acquisitions have been described as looking " like a speculator assembling a portfolio " . Æthelburh ' s possession of these lands foreshadows Cynethryth ' s control of religious lands , and the pattern was continued in the early ninth century by Cwoenthryth , the daughter of King Coenwulf . Either Offa or Ine of Wessex is traditionally supposed to have founded the Schola Saxonum in Rome , in what is today the Roman rione , or district , of Borgo . The Schola Saxonum took its name from the militias of Saxons who served in Rome , but it eventually developed into a hostelry for English visitors to the city . European connections . Offa ' s diplomatic relations with Europe are well documented , but appear to belong only to the last dozen years of his reign . In letters dating from the late 780s or early 790s , Alcuin congratulates Offa for encouraging education and greets Offa ' s wife and son , Cynethryth and Ecgfrith . In about 789 , or shortly before , Charlemagne proposed that his son Charles marry one of Offa ' s daughters , most likely Ælfflæd . Offa countered with a request that his son Ecgfrith should also marry Charlemagne ' s daughter Bertha : Charlemagne was outraged by the request , and broke off contact with Britain , forbidding English ships from landing in his ports . Alcuin ' s letters make it clear that by the end of 790 the dispute was still not resolved , and that Alcuin was hoping to be sent to help make peace . In the end diplomatic relations were restored , at least partly by the agency of Gervold , the abbot of St Wandrille . Charlemagne sought support from the English church at the council of Frankfurt in 794 , where the canons passed in 787 at the second council of Nicaea were repudiated , and the heresies of two Spanish bishops , Felix and Elipandus , were condemned . In 796 Charlemagne wrote to Offa ; the letter survives and refers to a previous letter of Offa ' s to Charlemagne . This correspondence between the two kings produced the first surviving documents in English diplomatic history . The letter is primarily concerned with the status of English pilgrims on the continent and with diplomatic gifts , but it reveals much about the relations between the English and the Franks . Charlemagne refers to Offa as his " brother " , and mentions trade in black stones , sent from the continent to England , and cloaks ( or possibly cloths ) , traded from England to the Franks . Charlemagne ' s letter also refers to exiles from England , naming Odberht , who was almost certainly the same person as Eadberht Praen , among them . Egbert of Wessex was another refugee from Offa who took shelter at the Frankish court . It is clear that Charlemagne ' s policy included support for elements opposed to Offa ; in addition to sheltering Egbert and Eadberht he also sent gifts to Æthelred I of Northumbria . Events in southern Britain to 796 have sometimes been portrayed as a struggle between Offa and Charlemagne , but the disparity in their power was enormous . By 796 Charlemagne had become master of an empire which stretched from the Atlantic Ocean to the Great Hungarian Plain , and Offa and then Coenwulf were clearly minor figures by comparison . Government . The nature of Mercian kingship is not clear from the limited surviving sources . There are two main theories regarding the ancestry of Mercian kings of this period . One is that descendants of different lines of the royal family competed for the throne . In the mid - seventh century , for example , Penda had placed royal kinsmen in control of conquered provinces . Alternatively , it may be that a number of kin - groups with local power - bases may have competed for the succession . The sub - kingdoms of the Hwicce , the Tomsæte , and the unidentified Gaini are examples of such power - bases . Marriage alliances could also have played a part . Competing magnates , those called in charters " dux " or " princeps " ( that is , leaders ) , may have brought the kings to power . In this model , the Mercian kings are little more than leading noblemen . Offa seems to have attempted to increase the stability of Mercian kingship , both by the elimination of dynastic rivals to his son Ecgfrith , and the reduction in status of his subject kings , sometimes to the rank of ealdorman . He was ultimately unsuccessful , however ; Ecgfrith only survived in power for a few months , and ninth - century Mercia continued to draw its kings from multiple dynastic lines . There is evidence that Offa constructed a series of defensive " burh s " , or fortified towns ; the locations are not generally agreed on but may include Bedford , Hereford , Northampton , Oxford and Stamford . In addition to their defensive uses , these " burhs " are thought to have been administrative centres , serving as regional markets and indicating a transformation of the Mercian economy away from its origins as a grouping of midland peoples . The " burhs " are forerunners of the defensive network successfully implemented by Alfred the Great a century later to deal with the Danish invasions . However , Offa did not necessarily understand the economic changes that came with the " burhs " , so it is not safe to assume he envisioned all their benefits . In 749 , Æthelbald of Mercia had issued a charter that freed ecclesiastical lands from all obligations except the requirement to build forts and bridges — obligations which lay upon everyone , as part of the trinoda necessitas . Offa ' s Kentish charters show him laying these same burdens on the recipients of his grants there , and this may be a sign that the obligations were being spread outside Mercia . These burdens were part of Offa ' s response to the threat of " pagan seaman " . Offa issued laws in his name , but no details of them have survived . They are known only from a mention by Alfred the Great , in the preface to Alfred ' s own law code . Alfred says that he has included in his code those laws of Offa , Ine of Wessex and Æthelberht of Kent which he found " most just " . The laws may have been an independent lawcode , but it is also possible that Alfred is referring to the report of the legatine mission in 786 , which issued statutes that the Mercians undertook to obey . Coinage . At the start of the eighth century , sceatta s were the primary circulating coinage . These were small silver pennies , which often did not bear the name of either the moneyer or the king for whom they were produced . To contemporaries these were probably known as pennies , and are the coins referred to in the laws of Ine of Wessex . This light coinage ( in contrast to the heavier coins minted later in Offa ' s reign ) can probably be dated to the late 760s and early 770s . A second , medium - weight coinage can be identified before the early 790s . These new medium - weight coins were heavier , broader and thinner than the pennies they replaced , and were prompted by the contemporary Carolingian currency reforms . The new pennies almost invariably carried both Offa ' s name and the name of the moneyer from whose mint the coins came . The reform in the coinage appears to have extended beyond Offa ' s own mints : the kings of East Anglia , Kent and Wessex all produced coins of the new heavier weight in this period . Some coins from Offa ' s reign bear the names of the archbishops of Canterbury , Jaenberht and , after 792 , Æthelheard . Jaenberht ' s coins all belong to the light coinage , rather than the later medium coinage . There is also evidence that coins were issued by Eadberht , who was bishop of London in the 780s and possibly before . Offa ' s dispute with Jaenberht may have led him to allow Eadberht coining rights , which may then have been revoked when the see of Lichfield was elevated to an archbishopric . The medium - weight coins often carry designs of high artistic quality , exceeding that of the contemporary Frankish currency . Coin portraits of Offa have been described as " showing a delicacy of execution which is unique in the whole history of the Anglo - Saxon coinage " . The depictions of Offa on the coins include a " striking and elegant " portrait showing him with his hair in voluminous curls , and another where he wears a fringe and tight curls . Some coins show him wearing a necklace with a pendant . The variety of these depictions implies that Offa ' s die - cutters were able to draw on varied artistic sources for their inspiration . Offa ' s wife Cynethryth was the only Anglo - Saxon queen ever named or portrayed on coinage - in a remarkable series of pennies struck by the moneyer Eoba . These were probably derived from contemporary coins from the reign of the Byzantine emperor Constantine VI , who minted a series showing a portrait of his mother , the later Empress Irene , though the Byzantine coins show a frontal bust of Irene rather than a profile , and so cannot have been a direct model . Around the time of Jaenberht ' s death and replacement with Æthelheard in 792 - 3 , the silver currency was reformed a second time : in this " heavy coinage " the weight of the pennies was increased again , and a standardised non - portrait design was introduced at all mints . None of Jaenberht ' s or Cynethryth ' s coins occur in this coinage , whereas all of Æthelheard ' s coins are of the new , heavier weight . There are also surviving gold coins from Offa ' s reign . One is a copy of an Abbasid dinar struck in 774 by Caliph Al - Mansur , with " Offa Rex " centred on the reverse . It is clear that the moneyer had no understanding of Arabic as the Arabic text contains many errors . The coin may have been produced in order to trade with Islamic Spain ; or it may be part of the annual payment of 365 mancuse s that Offa promised to Rome . There are other Western copies of Abbasid dinar s of the period , but it is not known whether they are English or Frankish . Two other English gold coins of the period survive , from two moneyers , Pendraed and Ciolheard : the former is thought to be from Offa ' s reign but the latter may belong either to Offa ' s reign or to that of Coenwulf , who came to the throne in 796 . Nothing definite is known about their use , but they may have been struck to be used as alms . Although many of the coins bear the name of a moneyer , there is no indication of the mint where each coin was struck . As a result the number and location of mints used by Offa is uncertain . Current opinion is that there were four mints , in Canterbury , Rochester , East Anglia and London . Stature . The title Offa used on most of his charters was " rex Merciorium " , or " king of the Mercians " , though this was occasionally extended to " king of the Mercians and surrounding nations " . Some of his charters use the title " Rex Anglorum , " or " King of the English , " and this has been seen as a sweeping statement of his power . There is debate on this point , however , as several of the charters in which Offa is named " Rex Anglorum " are of doubtful authenticity . They may represent later forgeries of the tenth century , when this title was standard for kings of England . The best evidence for Offa ' s use of this title comes from coins , not charters : there are some pennies with " Of ℞ A " inscribed , but it is not regarded as definite that this stood for " Offa Rex Anglorum . " In " Anglo - Saxon England " , Stenton argued that Offa was perhaps the greatest king of the English kingdoms , commenting that " no other Anglo - Saxon king ever regarded the world at large with so . . . acute a political sense " . Many historians regard Offa ' s achievements as second only to Alfred the Great among the Anglo - Saxon kings . Offa ' s reign has sometimes been regarded as a key stage in the transition to a unified England , but this is no longer the general view among historians in the field . In the words of Simon Keynes , " Offa was driven by a lust for power , not a vision of English unity ; and what he left was a reputation , not a legacy . " It is now believed that Offa thought of himself as " King of the Mercians , " and that his military successes were part of the transformation of Mercia from an overlordship of midland peoples into a powerful and aggressive kingdom . Death and succession . Offa died on 29 July 796 , and was buried in Bedford . He was succeeded by his son , Ecgfrith , but according to the " Anglo - Saxon Chronicle " Ecgfrith died after a reign of only 141 days . A letter written by Alcuin in 797 to a Mercian ealdorman named Osbert makes it apparent that Offa had gone to great lengths to ensure that his son Ecgfrith would succeed him . Alcuin ' s opinion is that Ecgfrith " has not died for his own sins ; but the vengeance for the blood his father shed to secure the kingdom has reached the son . For you know very well how much blood his father shed to secure the kingdom on his son . " It is apparent that in addition to Ecgfrith ' s consecration in 787 , Offa had eliminated dynastic rivals . This seems to have backfired , from the dynastic point of view , as no close male relatives of Offa or Ecgfrith are recorded , and Coenwulf , Ecgfrith ' s successor , was only distantly related to Offa ' s line .