It was not long ere Egbert had opportunities of displaying his natural and acquired talents.  Brithric, King of Wessex, had married Eadburga, natural daughter of Offa, King of Mercia, a profligate woman, equally infamous for cruelty and for incontinence.  Having great influence over her husband, she often instigated him to destroy such of the nobility as were obnoxious to her; and where this expedient failed, she scrupled not being herself active in traitorous attempts against them.  She had mixed a cup of poison for a young nobleman, who had acquired her husband’s friendship, and had on that account become the object of her jealousy; but unfortunately the King drank of the fatal cup along with his favorite, and soon after expired.  This tragical incident, joined to her other crimes, rendered Eadburga so odious that she was obliged to fly into France; whence Egbert was at the same time recalled by the nobility, in order to ascend the throne of his ancestors.  He attained that dignity in the last year of the eighth century.

In the kingdoms of the heptarchy, an exact rule of succession was either unknown or not strictly observed; and thence the reigning prince was continually agitated with jealousy against all the princes of the blood, whom he still considered as rivals, and whose death alone could give him entire security in his possession of the throne.  From this fatal cause, together with the admiration of the monastic life, and the opinion of merit attending the preservation of chastity even in a married state, the royal families had been entirely extinguished in all the kingdoms except that of Wessex; and the emulations, suspicions, and conspiracies, which had formerly been confined to the princes of the blood alone, were now diffused among all the nobility in the several Saxon states.  Egbert was the sole descendant of those first conquerors who subdued Britain, and who enhanced their authority by claiming a pedigree from Woden, the supreme divinity of their ancestors.  But that prince, though invited by this favorable circumstance to make attempts on the neighboring Saxons, gave them for some time no disturbance, and rather chose to turn his arms against the Britons in Cornwall, whom he defeated in several battles.  He was recalled from the conquest of that country by an invasion made upon his dominions by Bernulf, King of Mercia.

The Mercians, before the accession of Egbert, had very nearly attained the absolute sovereignty in the heptarchy:  they had reduced the East Angles under subjection, and established tributary princes in the kingdoms of Kent and Essex.  Northumberland was involved in anarchy; and no state of any consequence remained but that of Wessex, which, much inferior in extent to Mercia, was supported solely by the great qualities of its sovereign.  Egbert led his army against the invaders; and encountering them at Ellandun, in Wiltshire, obtained a complete victory, and, by the great slaughter which he made of them in their flight, gave a mortal blow to the power of the Mercians.  While he himself, in prosecution of his victory, entered their country on the side of Oxfordshire, and threatened the heart of their dominions, he sent an army into Kent, commanded by Ethelwulf, his eldest son, and, expelling Baldred, the tributary King, soon made himself master of that country.