The Percys supported the House of Lancaster during the Wars of the Roses, and the second earl and his successor – Henry Percy, 3rd Earl of Northumberland – were killed at the battles of St Albans in 1455 and Towton in 1461 respectively. The new king, Edward IV, issued an attainder against the family and their property was confiscated. On 1 August 1464, as a result of suppressing Lancastrian rebellions in the north for the previous three years, the title of Earl of Northumberland was given to The 1st Marquess of Montagu, a Yorkist, and with it, the castle. During his tenure, he constructed a twenty-five-foot tall rectangular tower, built for defence, "with [arrow] slits in the three outer walls;" this is known as 'Montagu's Tower' to this day. His brother, The 16th Earl of Warwick, used Warkworth as a base from which the Lancastrian-held castles of Northumberland – Alnwick, Bamburgh, and Dunstanburgh – were attacked and their sieges co-ordinated. In 1470 Edward IV returned the Percys' estates to the eldest son of the third earl, who was also called Henry Percy. A year later Henry was granted the earldom of Northumberland. Some time after 1472 Henry remodelled the building of the bailey. He also planned to build a collegiate church within the castle, but the work was abandoned after his death. When the fourth earl was murdered in 1489, his son, Henry Algernon, inherited and maintained the castle. In the early 16th century Henry Percy, 6th Earl of Northumberland, was responsible for clearing the collegiate church founded by his grandfather, but left incomplete by the fifth earl. Thomas Percy, brother of the sixth earl, was executed for his role in the Pilgrimage of Grace in 1536. When Henry Percy died the next year without any sons, the family's property passed to the Crown.