On the death of William Longsword, duke of Normandy, who had been assassinated by Arnulf, count of Flanders, in December 942, Louis endeavoured to obtain possession of the person of Richard, the young son and heir of the late duke.
In that year William Longsword, eldest of the five sons of Count William III., came to the kingdom of Jerusalem, on the invitation of Baldwin IV.
The original convent was destroyed by the Northmen, but was re-established by Duke William Longsword as a house of canons regular, which shortly afterwards was converted into a Benedictine monastery.
He had also three illegitimate sons: Geoffrey, archbishop of York; Morgan; and William Longsword, earl of Salisbury.
In the meanwhile the French feudatories on the left wing had thoroughly defeated the imperialists opposed to them, and William Longsword, earl of Salisbury, the leader of this corps, was unhorsed and taken prisoner by the warlike bishop of Beauvais.
Eventually, and long after the imperial army had begun its retreat, the gallant schiltron was ridden down and annihilated by a charge of three thousand men-at-arms. Reginald was taken prisoner in the melee; and the prisoners also included two other counts, Ferdinand and William Longsword, twenty-five barons and over a hundred knights.
Johns safety, however, was secured in a more practical way when his bastard brother, William, Longsword, earl of Salisbury, made a descent on the port of Damme and burnt or sunk a whole squadron of the French transports.
Of England; and the fables, her Ysopet, were written according to the Epilogus for a Count William, generally recognized to be William Longsword, earl of Salisbury.