Neville, respectively, the daughters of the Earl and Countess of Warwick and heirs to their mother's considerable inheritance. Many of the estates held by the brothers had been granted by Edward, who could also remove them, making them dependent on his favour. This was not the case with property acquired through marriage and explains the importance of this dispute. 1471 to 1483 The last significant rebellion ended in February 1474 with the surrender of John de Vere, 13th Earl of Oxford, who survived to command the Lancastrian army at Bosworth in 1485. Clarence was widely suspected of involvement, a factor in his eventual execution in the Tower on 18 February 1478; claims he was "drowned in a butt of Malmsey wine" appear to have been a joke by Edward, referring to his favourite drink. In 1475, Edward allied with Burgundy, and declared war on France. However, with Duke Charles focused on besieging Neuss, Louis opened negotiations. Soon after Edward landed at Calais, the two signed the Treaty of Picquigny. Edward received an immediate payment of 75,000 crowns, plus a yearly pension of 50,000 crowns, thus allowing him to recoup the costs of his army. In 1482, Edward backed an attempt to usurp the Scottish throne by Alexander Stewart, 1st Duke of Albany, brother of James III of Scotland. Gloucester invaded Scotland and took the town of Edinburgh, but not the far more formidable castle, where James was being held by his own nobles. Albany switched sides and without siege equipment, the English army was forced to withdraw, with little to show for an expensive campaign, apart from the capture of Berwick Castle. Edward's health began to fail, and he became subject to an increasing number of ailments; his physicians attributed this in part to a habitual use of emetics, which allowed him to gorge himself at meals, then return after vomiting to start again. He fell fatally ill at Easter 1483, but survived long enough to add codicils to his will, the most important naming his brother as Protector after his death. He died on 9 April 1483 and was buried in St George's Chapel, Windsor Castle. His twelve-year-old son, Edward V, was never crowned, Gloucester becoming King Richard III in July. The cause of Edward's death is uncertain; allegations of poison were common in an era when lack of medical knowledge meant death often had no obvious explanation. Other