Later in this year William’s final warfare for the kingdom began.  In August, 1069 the long-promised help from Denmark came.  Swegen sent his brother Osbeorn and his sons Harold and Cnut, at the head of the whole strength of Denmark and of other Northern lands.  If the two enterprises of Harold’s sons had been planned in concert with their Danish kinsmen, the invaders or deliverers from opposite sides had failed to act together.  Nor are Swegen’s own objects quite clear.  He sought to deliver England from William and his Normans, but it is not so plain in whose interest he acted.  He would naturally seek the English crown for himself or for one of his sons; the sons of Harold he would rather make earls than kings.  But he could feel no interest in the kingship of Edgar.  Yet, when the Danish fleet entered the Humber, and the whole force of the North came to meet it, the English host had the heir of Cerdic at its head.  It is now that Waltheof the son of Siward, Earl of Northampton and Huntingdon, first stands out as a leading actor.  Gospatric too was there; but this time not Edwin and Morkere.  Danes and English joined and marched upon York; the city was occupied; the castles were taken; the Norman commanders were made prisoners, but not till they had set fire to the city and burned the greater part of it, along with the metropolitan minster.  It is amazing to read that, after breaking down the castles, the English host dispersed, and the Danish fleet withdrew into the Humber.

England was again ruined by lack of concert.  The news of the coming of the Danes led only to isolated movements which were put down piecemeal.  The men of Somerset and Dorset and the men of Devonshire and Cornwall were put down separately, and the movement in Somerset was largely put down by English troops.  The citizens of Exeter, as well as the Norman garrison of the castle, stood a siege on behalf of William.  A rising on the Welsh border under Eadric led only to the burning of Shrewsbury; a rising in Staffordshire was held by William to call for his own presence.  But he first marched into Lindesey, and drove the crews of the Danish ships across into Holderness; there he left two Norman leaders, one of them his brother Robert of Mortain and Cornwall; he then went westward and subdued Staffordshire, and marched towards York by way of Nottingham.  A constrained delay by the Aire gave him an opportunity for negotiation with the Danish leaders.  Osbeorn took bribes to forsake the English cause, and William reached and entered York without resistance.  He restored the castles and kept his Christmas in the half-burned city.  And now William forsook his usual policy of clemency.  The Northern shires had been too hard to win.  To weaken them, he decreed a merciless harrying of the whole land, the direct effects of which were seen for many years, and which left its mark on English history for ages.  Till the growth of modern industry reversed the relative position of Northern