The exact period when this fortress was erected is unknown; though some circumstances render it probable that it was built by King Edgar. That it did not exist previously to the year 887, or 888, the time when the Nunnery at Shaftesbury was founded, is certain, from an inquisition taken in the fifty-fourth of Henry the Third; wherein the jurors returned, "that the Abbess and Nuns at Shaston (Shaftesbury) had without molestation, _before the foundation of the Castle at Corfe_, all wrecks within their manor of Kingston, in the Isle of Purbeck." Mr. Aubrey, in his _Monumenta Britannica_, observes, he was informed, "that mention was made of Corfe Castle in the reign of King Alfred; yet it seems very improbable that this should be the fact; for if it had actually existed in the time of that monarch, it would surely have been more publicly known. The short reigns that succeeded would not allow time for so extensive an undertaking; but Edgar enjoyed more peace than almost any of his predecessors, was superior in wealth and power, and a great builder; he having founded, or repaired, no fewer than forty-seven monasteries." To him, then, the origin of this castle may with the greatest probability be ascribed, as his second wife, Elfrida, resided here at the commencement of her widowhood. During this residence was committed the foul murder on King Edward, Edgar's son and successor, of which William of Malmesbury relates the ensuing particulars. "King Edward being hunting in a forest neare the sea, upon the south-east coast of the countie of Dorset, and in the Isle of Purbecke, came neare unto a fair and stronge castell, seated on a little river called Corfe, wherein his mother-in-law, Elfrida, with her sonne Ethelred, then lived: the King, ever beareing a kinde affection to them, beeing soe neare, would needs make knowne soe much by his personall visitation; which haveing resolved, and beeing either of purpose or by chance, singled from his followers, hee rode to the Castell gate. The Queene, who long had looked for an opportunitie, that, by makeing him awaye, shee might make waye for her own sonne to the Crowne, was glad the occasion nowe offered itselfe; and therefore, with a modest and humble behaviour, she bade him welcome, desireing to enjoye his presence that night. But hee, haveing performed what hee purposed, and doubting his companie might find him misseing, tolde her, that he now intended on horseback to drink to her and his brother in a cuppe of wine, and soe leave her; which beeing presented unto him, the cuppe was no sooner at his mouth, but a knife was at his back, which a servant, appointed by this treacherous woman, stroke into him. The Kinge, finding himselfe hurt, sett spurs to his horse, thinking to recover his companie; but the wounde beeing deepe, and fainting through the losse of much blood, he felle from his horse, which dragged him by one foot hanging in the stirrop, untill he was left dead at Corfe gate, Anno Dom. 979."