Meanwhile, George's health deteriorated. He developed dementia, and became completely blind and increasingly deaf. He was incapable of knowing or understanding that he was declared King of Hanover in 1814, or that his wife died in 1818. At Christmas 1819, he spoke nonsense for 58 hours, and for the last few weeks of his life was unable to walk. He died at Windsor Castle at 8:38 pm on 29 January 1820, six days after the death of his fourth son Prince Edward, Duke of Kent and Strathearn. His favourite son, Frederick, Duke of York, was with him. George III was buried on 16 February in St George's Chapel, Windsor Castle.