Pursuing a conciliatory policy with Lancastrian families, King Edward allowed John de Vere to succeed his father, and on 18 January 1464 granted him licence to enter on his father's lands. On 26 May 1465 he was created a Knight of the Bath at the coronation of Edward IV's wife, Elizabeth Woodville, and officiated at the ceremony as both Lord Great Chamberlain, in the absence of the then office-holder, the Earl of Warwick, and as Chamberlain to the queen. In November 1468, however, he was committed to the Tower, and confessed to plotting with the Lancastrians against the King. He was likely released before 7 January 1469, and received a general pardon on 5 April of that year. However, by early July 1469 Oxford had joined the discontented Yorkists led by his brother-in-law, the Earl of Warwick, and King Edward's brother, the Duke of Clarence, for the Edgecote campaign. Following the loss at Edgecote on 12 March 1470, he fled overseas to the court of King Henry VI's wife, Margaret of Anjou. In September 1470 he joined Warwick and Clarence in the invasion of England which restored Henry VI to the throne, and on 13 October bore the Sword of State before Henry in a procession to St Paul's. He was appointed Lord High Constable of England, and as such on 15 October tried and condemned for high treason the same Earl of Worcester who had in 1462 condemned Oxford's own father and brother.