But while Offa was hampered in his projects by the dread of the West Saxons at home, he was forced to watch jealously a power which had risen to dangerous greatness over sea, the power of the Franks. Till now, the interests of the English people had lain wholly within the bounds of the Britain they had won. But at this moment our national horizon suddenly widened, and the fortunes of England became linked to the general fortunes of Western Christendom. It was by the work of English missionaries that Britain was first drawn into political relations with the Frankish court. The Northumbrian Willibrord, and the more famous West-Saxon Boniface or Winfrith, followed in the track of earlier preachers, both Irish and English, who had been labouring among the heathens of Germany, and especially among those who had now become subject to the Franks. The Frank king Pippin's connexion with the English preachers led to constant intercourse with England; a Northumbrian scholar, Alcuin, was the centre of the literary revival at his court. Pippin's son Charles, known in after days as Charles the Great, maintained the same interest in English affairs.

His friendship with Alcuin drew him into close relations with Northern Britain. Ecgberht, the claimant of the West-Saxon throne, had found a refuge with him since Offa's league with Beorhtric in 787. With Offa too his relations seem to have been generally friendly. But the Mercian king shrank cautiously from any connexion which might imply a recognition of Frankish supremacy. He had indeed good grounds for caution. The costly gifts sent by Charles to the monasteries of England as of Ireland showed his will to obtain an influence in both countries; he maintained relations with Northumbria, with Kent, with the whole English Church. Above all, he harboured at his court exiles from every English realm, exiled kings from Northumbria, East-Anglian thegns, fugitives from Mercia itself; and Ecgberht probably marched in his train when the shouts of the people and priesthood of Rome hailed him as Roman Emperor. When the death of Beorhtric in 802 opened a way for the exile's return to Wessex, the relations of Charles with the English were still guided by the dream that Britain, lost to the Empire at the hour when the rest of the western provinces were lost, should return to the Empire now that Rome had risen again to more than its old greatness in the west; and the revolutions which were distracting the English kingdoms told steadily in his favour.

The years since Ecgberht's flight had made little change in the state of Britain. Offa's completion of his kingdom by the seizure of East Anglia had been followed by his death in 796; and under his successor Cenwulf the Mercian archbishopric was suppressed, and there was no attempt to carry further the supremacy of the Midland kingdom. Cenwulf stood silently by when Ecgberht mounted the West-Saxon throne, and maintained peace with the new ruler of Wessex throughout his reign. The first enterprise of Ecgberht indeed was not directed against his English but his Welsh neighbours. In 815 he marched into the heart of Cornwall, and after eight years of fighting, the last fragment of British dominion in the west came to an end. As a nation Britain had passed away with the victories of Deorham and Chester; of the separate British peoples who had still carried on the struggle with the three English kingdoms, the Britons of Cumbria and of Strathclyde had already bowed to Northumbrian rule; the Britons of Wales had owned by tribute to Offa the supremacy of Mercia; the last unconquered British state of West Wales as far as the Land's End now passed under the mastery of Wessex.

While Wessex was regaining the strength it had so long lost, its rival in Mid-Britain was sinking into helpless anarchy. Within, Mercia was torn by a civil war which broke out on CenwulPs death in 821; and the weakness which this left behind was seen when the old strife with Wessex was renewed by his successor Beornwulf, who in 825 penetrated into Wiltshire, and was defeated in a bloody battle at Ellandun. All England south of the Thames at once submitted to Ecgberht of Wessex, and East Anglia rose in a desperate revolt which proved fatal to its Mercian rulers. Two of its kings in succession fell fighting on East-Anglian soil; and a third, Wiglaf, had hardly mounted the Mercian throne when his exhausted kingdom was called on again to encounter the West-Saxon. Ecgberht saw that the hour had come for a decisive onset. In 828 his army marched northward without a struggle; Wiglaf fled helplessly before it; and Mercia bowed to the West-Saxon overlordship. From Mercia Ecgberht marched on North-umbria; but half a century of anarchy had robbed that kingdom of all vigour, and pirates were already harrying its coast; its nobles met him at Dore in Derbyshire, and owned him as their overlord.

The work that Oswiu and aethelbald had failed to do was done, and the whole English race in Britain was for the first time knit together under a single ruler. Long and bitter as the struggle for independence was still to be in Mercia and in the north, yet from the moment that Northumbria bowed to its West-Saxon overlord, England was made in fact if not as yet in name.