Yves de Vescy, Baron of Alnwick, erected the first parts of the castle in 1096. It was built to defend England's northern border against the Scottish invasions and border reivers. It was besieged in 1172 and again in 1174 by William the Lion, King of Scotland and William was captured outside the walls during the Battle of Alnwick. In 1309 it was bought from Antony Bek the Bishop of Durham by Henry de Percy, 1st Baron Percy and it has been owned by the Percy family, the Earls and later Dukes of Northumberland since then. The first Percy lord of Alnwick restored the castle and the Abbot's Tower, the Middle Gateway and the Constable's Tower survive from this period. In 1404-5 the Percys rebelled against Henry IV, who besieged and then took the castle.